There's a whole lot of nonsense in terms of the battles and the geography (look at a map before you go on about Angmar and Gundabad!). There's some completely pointless changes that piss off the purists while not doing anybody else any good (Azog is supposed to be long dead by this time, it's all about his son Bolg seeking revenge, instead of having them both side by side as in the movies, while Aragorn is all of ten years old so hardly known as 'Strider' just yet). There's eyeroll-worthy comic relief (Alfrid and Stephen Fry's take on the Master of Laketown, arguably also Radagast though he kinda works for me). There's some 'woke' changes, like Galadriel singlehandedly defeating Sauron at Dol Guldur with the rest of the White Council no more than glorified bodyguards, or Evangeline Lilly's character Tauriel and her Elf-Dwarf romance storyline that Tolkien almost certainly wouldn't have approved of. There's Legolas getting a ridiculous amount of screentime (most of it involving said battle nonsense) for an adaptation of a book he's never even mentioned in, what with not having been invented yet.

But for all that, the movies aren't that bad and still loads better than RoP (the first season, still didn't see any of the second but it doesn't sound like it's improved any). Because the basics of the storyline still stand and the development of the characters is largely what it should be, with solid performances especially in the key roles Thorin, Bilbo and Smaug. Even Tauriel's budding romance with Kili ends with his death before it even really starts, so doesn't really violate canon all that much.

Of course, the RoP writers didn't have a book like The Hobbit to follow - but as I said elsewhere, their problems have as much to do with them being too afraid to come up with their own characters and plotlines, as with them taking too many liberties with the canon.