Grainne has tons of amazing answers. You can look at their replies to questions and get amazing answers.
Pet taming is a lot easier than we remember and you get multiplies. It doesn’t hurt to make a second hunter and level it thru the guided experience. Since you have an 80, you won’t be able to get the newbies in-game channel (unless they changed it). Really, don’t hesitate to let this character be parked for a bit.
My priority on returning:
Figure out game mechanics again. Talent trees are more complex. Initially, you can run with starter build to not worry about it. You can also add builds, swap specs, etc with no penalty. The days of having to level multiple characters to play all the specs are done and you don’t have to kill gold to respec. I really like this feature.
Mobs level with you (up to a point). I initially didn’t like this, but now I do. I still don’t entirely understand the rules, but it keeps things fresh.
The shielded quests are the big ones you must do to advance the story. Dragon isles seems more rigid here and you get buried in cosmetics (I did not love this). If you get overwhelmed, just focus on the shielded quests (story / campaign are other terms that show up).
The AI dungeons can be great to learn the new mechanics. There’s more stuff to move from, more things on the ground, and PUGs can sometimes move obscenely fast. I used these to get comfortable and go at my own pace. If you’re learning tanking or healing, these can also help.
The flying really does take some time to get used to. I’ve stuck with it, even tho it annoys me because it really is faster and eventually the dynamic nature becomes fun (until you screw up and just need to wait for vigor to come back). The dragon characters also get it early and I like the soar feature (I also main a druid, so flight form over all).
I’ve accepted there’s a level of story that I may never fully catch up on. Lore walking can fill in some gaps. I’m an impatient leveler, so I’ve only now gotten into that a bit. YMMV.
Undercity and Darnassus have phased versions you can still access, but the short of it is they did the Banshee Queen dirty and she blew everything up. Make sure to hit the time -warped version before going there - they do try to guide you but I’ve ended up dying there a few times. Take the portal, not the teleporter in Silvermoon.
There’s a 1 button DPS button you can use to learn rotations, as well as highlighting. If you drag the button out somewhere, you can also use it if playing off spec or dealing with overwhelm. It’s pretty reasonable. Again, dungeons have more stuff to memorize.
I still cannot find certain things and still do a LOT of googling. It does get better, but it’s a lot. I’m also learning Korean (one of the hardest languages for an English speaker to learn) and the difficulty of that and re-learning this game do feel on par. It’s just going to take time and patience helps a lot.
I intentionally level alts along the same path right now to reduce overwhelm. I found that helped me. Again, YMMV.