But that's the point - WoW isn't designed to be played with strangers. It's an old school MMORPG where you're supposed to form organized groups to tackle the hardest content. M+ made this paradigm basically worthless imho (but i may be completely wrong and i'm not making M+ guilty of anything).
I can agree with difficulty tuning. Too punishing makes for a worse experience for everyone involved. Gear scaling, a little less as you can get near-ilvl cap gear by running 15s.
As much as i don't get why people buy boosts (but i'm starting to get a very clear idea of the whole thing) i don't get why people expect to have all content just puggable. It's not a single player game. Hell, if it wasn't for the nice groups of people i have played with during these 17 years, i would have stopped playing much sooner.
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But raids are terrible to get gear from. M+ is much faster and accessible and rewarding. Enrage timers are not existant anymore, i have had groups where most people parsed grey and we still killed the boss. I agree that in SL raid mechanics were overwhelming in much occasions but SL is also an exception in how overtuned it has been.
People have always put up barriers to find better people for their groups, and it's natural. However, if people are fine to get boosted to do stuff, then these barriers are useless.