Honestly that's probably half because of how insanely forgiving literally everything outside actual current endgame raiding is more than anything. Like low dps will absolutely make a run noticeably slower, but me personally I usually just don't care enough to say or do anything about it unless the person is literally doing nothing.
What's wild is, while I have absolutely seen people do that (shout-out to that one whm that spent almost an entire e6 running around doing mechanics but casting nothing????) It's also just... Generally easier to ignore in this game. Maybe part of that IS because I don't have numbers on my screen telling me someone is performing abysmally, but I also... don't really need the numbers to be able to tell most of the time. Idk. It's interesting to think about.
But I also think I'm a lot more mellow now than I was when I played, say, WoW. Even then I probably kicked as many people for whining about dps as I did for doing bad (read: literally afk) dps so I mean : p shrug lmao