Hey OP, I feel ya. One of the most difficult parts of an MMO is finding the guild/group of people that we connect with and create a positive environment for everyone. If we look hard enough I think the toxicity is there in most MMOs. You mention wow classic, and I dont think there has been a more backstabbing, toxic, soul crushing environment as unlocking AQ40 and the race for scarab lord. Also, the PVP in that game in order to get to rank 14 sounds so horrible it would be difficult not to live off the salt.
Something I found helpful was to find new growing guilds to jump onto. Maybe there weren't doing the same content as me, but I could guide them through said content and those individuals made the game far more enjoyable.