Like everything else in the game it's RNG. I will straight up leave a group if we die 25 times before the first boss and I have no regret about it.
Some people stick it out and are cool, some people ragequit and ruin keys.
Overall it's kind of a curve, like lower level keys are much easier to get into but have a lot of dumbasses as well, once you get to around 10 keys people start taking the game super cereal but overall they've been smoother for my alts. However I can carry the entire group if the key is like a +4. 15s you start getting meta only groups that you just will not get into if you're not the right spec, making you have to make your own keys.
m+ is easy enough, some weeks are much more brutal than others but anything below a 10 is honestly pretty doable for most casual players.