A good player isn'a bad player I guess.
So they use their skills, know how their job works. Learns from mistakes by self teaching or from being "called out" and doesn't bail. Theyre willing to learn basically.
They don't make life difficult for others.
They might not necessary have the most optimum rotation going but they're tanking/healing/dpsing and we are killing enemies and clearing the dungeon without much hassle.
-Tank loses enmity? So what. Probably my fault as diversion was on cooldown and I forgot to pop Lucid. We still killed it and moved on with no hassle.
-Healer let DPS die as they were DPSing too? No biggie, just swiftraise and we carry on as we were. That's why those two skills are there after all and well done healer for DPSing too.
-DPS isn't hitting an optimum rotation but is still throwing AOE and using their arsenal and we are killing everything? Cool. So what if we spent 47 seconds more on that section between bosses because your rotation was wrong or you used X instead of Y then. I don't mind. I'm here to have fun and not stress over stuff like that.
I consider myself a good player but then I haven't touched a single savage nevermind ultimate fight. Does that mean I'm untested and subsequently an awful player? I doubt it.