I've played more than it sounds like you have (I started near the end of the Burning Crusade cycle and then subscribed pretty much constantly for four years, quitting about halfway through Cataclysm's cycle), but I have many of the same feelings.

On the combat side of things, everything is incredibly easy now. I used to have to strategize any encounter involving more than one enemy, and when I pulled off feats of survival against difficult foes and situations with my hunter it felt neat. Now, as you said, combat is essentially trivial outside of dungeons. I enjoy soloing things, I'm not so big on the community aspect as you, but there's no challenge to it and that robs it of some of its meaning and enjoyment and turns it into a quick grind from 1 to 85, with the tacit implication that the game only really begins at max level when you do dungeons. But dungeons get old for me, and the first time I hit the minimum Northrend level when I was still in the third Outland zone, I knew something was wrong.

On the world side, I used to love bombing around and exploring while I quested, or just for the fun of it. I thought that opening up Azeroth to flying mounts would make that even more fun, but instead it killed my enjoyment on that side as well. Suddenly everything was just ... there. Open and available without effort. And I stopped caring. Even when you're on-level with no flying mount, the questing experience from 1-60 is on rails these days. You never have to go exploring. You get automatically shuttled from one quest hub to the next, do a few things in the immediate area around the new one, then get shuttled on, repeat until Outland. The zones stopped feeling alive to me and started feeling like set-pieces for the game's quest infrastructure.

So all in all I'm not tempted to go back either, even though I appreciate that they finally added account-wide mounts, pets, and achievements. I would have loved that addition back in the day.

I'm still playing Lord of the Rings Online though. I subscribed to it enough that now I can play most of it for free, and the game is still large enough, slow enough, and challenging enough that I'm still only on the verge of hitting the first expansion area (out of three, with a fourth coming next month). I don't do community or group stuff there either, but I appreciate that it's a game that gives me challenge and exploration at whatever pace I want.