>>535993790
From someone who is maximum mazed
>Classic Era
permanent classic, its semi dead but there's still a population of about 10k you'll struggle to find groups for endgame content if you're not willing to trawl discord
>Classic Anniversary
progressive classic server currently about 3/4ths of the way through classic and will go on to TBC some time next year, its not dead but starting out fresh can be hard and you will probably still need to join a group
>MoP Classic
Just started last month, its only 2 raid resets in but be aware the economy is fucked, has double the population of anniversary so groups are easy to find right now though
>Retail
End of the current expansion you have about 9 months til the next one so plenty of time to experience everything and jump in, the primary disadvantage of getting in to retail is you have 20 years of disconnected expansions with no narrative thread holding them together and heaps of abandoned systems, the game will start you off in dragonflight but constantly reference past events and call you champion, unless you watch catchup videos you will likely have no idea what is going on and feel no connection to any of it, endgame gearing is shit but faster than past expansions
Something to note every single iteration of classic (not MoP just vanilla) has the worst community imaginable, classic can be beaten by a blind man with his hands tied behind his back slamming his face in to the keyboard and yet every single group will insist that you minmax to hell and back if you want to join them, the only way to avoid this is to find a friendly guild and join their discord and ask them to take you along knowing you're not minmaxed
My recommendation is to start MoP since its early in, once you get the hang of the game if you like it you can either go try out Classic anniversary before TBC drops or retail depending on which looks more appealing