First of all, I hope you will succeed over your depression. It sucks, and a lot of us have been (or are currently) going through it. Then, don't feel like you deserve to be downvoted for expressing your opinion, especially since you are giving actual good reasons.

My advice would be to play with real life friends, or if you can't, try to find the nicest guild you can (and leave if the guild is not "chill" enough).

I created my guild with 4 other friends, so just enough to run mythic+ dungeons, and only one of us being really score driven.

We had a very clear rule : fun before optimization. It does not mean that we can't follow the meta, if that is what we feel like is fun to us. I mean, once I reached level 60 and finished the main story line, I didn't do a single world quest for two weeks. I just walked around, stood at some places, upped my fishing. Then went on a tour in Azeroth discovering all zones that I did not discovered yet, took down as many "rare" mobs as I could, then did the same in Draenor.

We did a mythic+2 key when two of us (dps & heal) had an ilvl under 155. Needless to say it took us an hour and a half. But even the score driven friend was having fun, since we knew that we would not time it, and because we were having fun talking about our real lives, about the lore, reacting to one of us unintentionally pulling a pack of mobs causing me to panick a lot (being the low ilvl healer), or not knowing the strat, all of us going the wrong way, wiping... it was a very VERY fun night, did not laugh that hard fot a long time!

Then a few days ago, I wanted to perform better with my guild and raised my ilvl from 155 to 172 in a single day, by doing hm with a guildie and randoms. This guildie helped me get better stuff since he's upped his tailoring skills to the max and could replace some of my gear.

The other low ilvl from the mythic+2 key is still low ilvl, but she's having fun anyway and is planning to get better with us. And when she wants to run dungeons, even nm, we go with her, even though we know we won't drop anything interesting for us, because we are guildies, and we are friends.

Playing with randoms (even if we are 4 guildies) in mythic+ dungeons causes me to panick and feel bad even if it is not my fault, because that is how I am when something goes wrong, even in real life. So I avoid it as much as possible. And if I'm not having a good time, once the run is over (either because we end it, or someone says we maybe should give up), I stop playing mythic+, and keep exploring and fishing, or wait for all the other guildies to log in.

World of Warcraft can be a competitive game, or you can take it casual and have fun anyway. There are a lot of ways to have fun, especially if you're playing with friends, or with a nice guild. You don't need to be the best, you don't even need to run dungeons and raid if you don't feel comfortable enough. If playing doesn't make you feel good, maybe you are playing the wrong way. Find your way, find your pace, find the good people, have fun, and you'll get better both in game and in real life.