If you haven't already, I'd check out the guild recruitment section of the forums or else scroll through the guild finder in-game. There are tons that advertise being friendly for new and returning players.

From last year to this, the antiquities system was introduced and I know Alcast has a guide about it as well as info on all the mythics, and I'm sure other content creators will have information on them as well. Mythic items are very strong so you'll want to invest in the antiquities system if you bought Greymoor or sub with ESO+.

The other biggest change was CP 2.0, and the best advice for you there, as someone who was also a returning player at a loss in the new system, is to follow someone else's build (all of the youtubers above will probably include CP allocation in their builds), then once you have a feel for it change how you allocate and slot to fit your own playstyle. Also, don't forget to slot stars and confirm your changes afterward, as I and so many others have done.