IIRC, Martin didn't even try to make up languages. He has whatever words he needed at the time for Dothraki and High Valyrian, and frankly admited that there was no language or vocabulary set down for reference. He's plainly using the different languages for atmosphere and plot devices, not to convey an accurate representation of a made-up world. Generally characters just mention that someone is speaking a certain language, if they don't understand, or if they also speak it, it just says which language they are speaking. There are a couple of words, like the 'valar morghulis' phrase, which were plainly made to sound cool, rather than adhere to rules of language. The closest I can think of Martin doing anything like playing linguist is all the Dothraki titles, like khal, khaleesi, ko, and so on, which don't really seem to be too implausible. For a patriarchal culture, in which women are afterthoughts and appendages, politically speaking, it seems appropriate to have the feminine form of a title to look something like a dimunitive, regardless of how Mongolian or Turkish handles that issue.

For Jordan, he is plainly conscious of, and reacting to, fan feedback, and felt the need to be able to say "yes, I have the Old Tongue all planned out", no matter how poorly he did so. But given his addiction to detail, he needed to be able to have some words on the page when it was called for. The defense that maybe the normal speech in WoT sounds like the Old Tongue, so it didn't necessarily evolve into English founders on the point that characters sometimes make puns using English-Old Tongue homonyms, like toe and toh. But I still think it makes a better story if the characters are making references to ji'e'toh instead of The Honor Code, or Tel'Aran'Rhiod and saidar/saidin rather than "Dreamworld" or "male magic" and "female magic". It's half-assed completism that he tried to explain where the names of these concepts came from, without having the knowledge to properly develop the details of that language to satisfy the people who understand the mechanics.

What's more, while it's obivous that a lot of stuff is highly derivative of real world cultures, wouldn't that make sense as a narrative shortcut, given how excessive they take most of their world-building? If Braavos is ripped off from Venice, doesn't that spare Martin the trouble of coming up with all new stuff on his own, while maintaining a degree of verisimiltude? I read somewhere that Elmore Leonard often used pop culture references in his books in lieu of dialog, so that instead of describing a character or his clothing, another character would say "He looks like Clint Eastwood" or that he was wearing a hat & coat like Humphrey Bogart in the Maltese Falcon. By giving enough clues that you could figure out what country Martin or Jordan is basing a setting in his book upon, doesn't that give you a better grasp of an identity for that fake country? Can we really call Jordan a hack for sticking bits of Japanese culture in the Borderlands in the same book where Thom refers to legends that are plainly Easter-egg references to our world & time?

Well it's not very common in English, at least not as frequently used as many other vowel combinations, so it seems foreign. It seems to also be the rule behind pig Latin, which I never understood until I took Latin courses and realized the -ay suffix might actually be -ae, as in first declension genitive & nominative plural, which are two fairly important tenses, and thus a lot of people would associate words ending in a long A sound with Latin. The old English thing, I think it was called 'ash', like in archaic spellings of 'encyclopedia' might also mean that people associate 'ae' with old fashioned stuff. Like the way they write "ye olde shoppe".
Is that important to a good book, or an entertaining story, though? I understand the problem when real world understanding of a concept or subject or discipline can yank you out of the story, but that's just something you have to learn to get past, like people seeing their jobs depicted in film and TV. Or their hobbies and other interests. One of my brothers is fascinated by European aristocracy and his biggest complaint about "Game of Thrones" without ever having read the books, is how un-aristocratic the nobles behave on the show, and in particular, how graceless and low-class Cersei moves and acts.

I don't think it's so important to sound old, as to simply give it a flavor. I don't know how well Jordan and Martin followed old rules of grammar or customs of speech, but they made it sufficiently consistent that I could definitely tell how badly Sanderson failed to do the same thing, with his mixing in modern technical jargon with archaic styles of speech that were far more exaggerated and absurd than anything Jordan or Martin ever wrote. "My thanks," for instance, may or may not be historically correct or accurate, but it is not how Emond's Fielders talk in WoT, so when he has Egwene say it, it just stands out. Likewise for using "one" as a first person pronoun. I don't know if that was how people actually talked in any time or place, or if it's just Sandersonian idiocy, but when Cadsuane only starts doing it in her first appearance in a Sanderson book, it jumps out far worse than Jordan's or Martin's failures to adhere to how people talked in the real world. It would be one thing if Bernard Cornwell was making such mistakes in the Saxon Chronicles, but WoT and aSoI&F are not attempting to show how people talked in the real world in a certain period, they are simply attempting to have their own flavor of speech, so we don't have the even more distractingly anachronistic contemporary speech in such an alien setting.
Which would be a legit criticism of someone attempting to demonstrate how people spoke a long time ago. But he's not. He's trying to show how people spoke in a world he made up to be the setting for a family of children who find a litter of giant baby wolves.
IDK, speaking as a relgious person, getting belief in stories wrong is often worse than not having it. Maybe there should be some religion in the background or something, with the main characters simply not partaking, but given Jordan's explanation of what he thinks religious belief is all about, I'm just as glad he didn't try writing about characters who believe as he clear does not. And I agree it does detract from the characterization that most of them do not identify with anything really at all. Not a country, or a people or a belief system or a specific code or anything. In fact, most of the 'believers' in anything in WoT are actually background antagonists. The good guys have no factions or sides, they just are, as if there is something superior about not holding any position or anything. It just doesn't feel right about them, but on the other hand, it's more annoying, sometimes even insulting, when someone who just doesn't get it, tries to replicate that mindset.

Speaking of the language issue though, I do not know if you are familiar with Harry Turtledove's "Darkness" series. Turtledove is one of those authors who is credited with a great imagination, but his alternate worlds and fantasy setting are really nothing more than historical events in different places with names changed around.

So with that in mind, he made a fantasy series, which was basically World War Two, but with magic replacing electronics, technology and physics, and alchemy instead of chemistry. In order to create the "feel" or "flavor" of a multi-national/ethnic/lingual continent, he simply substituted real-world langauges. All the dialogue was in English, when the PoV character didn't understand a language, he simply noted that the foreigners were talking in their own language, but from place and personal names, it is easy to see what the languages are supposed to be.

Obviously, this does create distinctions to the reader's eye that are easy for the author to maintain when naming characters or locations, but it makes little sense, historically speaking. Lithuanian is their equivalent of Latin, while French is represented by Latvian. Furthermore, another country ALSO speaks Latvian, despite the two nations being on seperate peninsulas, one of which is further isolated from the continent by an alpine-like mountain range. Meanwhile, in the centuries since these countries' mutual language evolved from Lithuanian to Latvian, Lithuanian was used throughout the continent as a common language of academia, diplomacy & science AND was retained as the speech of a minority group of this same ethnic race, who were isolated among another country's population directly analogous to the Jewish communities of Eastern Europe, only if they spoke Hebrew instead of Yiddish. What's worse, is that their equivalent of the Roman Empire, which spoke Lithuanian in ancient times, rather than oriented around a central sea, and primarily located in coastal regions and peninsulas, was a vast inland empire. It's like Ancient Rome was spread much further north in Europe, and then when the Germans and Slavs came in and broke it up, the ethnic & cultural Romans held onto Italy & the Balkans even after the fall of the Empire, but their language changed to French, while communities of people speaking Latin and identifying as Romans were scattered through Germany & Eastern Europe. And this state of affairs lasted up through World War Two, while Latin retained its cultural significance even outside of the reach of the old Roman Empire, with Russians and Fins and Turks all using Latin to communicate formally, while Chinese, German, Scandinavian and Arabic scientists used Latin professionally. When a Latvian-speaking PoV character is talking to a Lithuanian-speaking couple, their dialogue is represented in English as archaic, with "thee"s and "thou"s.

Linguistically, it seems very suspect, as does the described degree of divergence of appearance of ethnic groups, whereby you can instantly identify a Pole or a Frenchman or a German at a glance, and Jews have to use magic to conceal their physical appearances to sneak out of their equivalent of the Warsaw ghetto. On the other hand, it drives home to readers the differences between nationalities without having to phonetically describe their accents.

For more obscure scholastic disciplines, I think sometimes we have to let things slide, like physics in Star Wars, if it advances the narrative purpose.