I understand how some people get frustrated that they join a roulette queue in the DF and end up with new people in a group that wipe on something that they, themselves, know very well. I understand that brief moment of "aaaauugh!" because something you thought would be quick turned into something lengthy. But to get pissy at people for it is ridiculous. Just teach the new players, explain the mechanics. There are very few fights in this game that can't be explained in a pretty simple manner
(EX fights are another story but I'm going to assume that if you want to farm EX primals you join a PF for that and I do understand being angry when someone new joins a farming PF party but that's a different discussion.)

It's especially jarring to see people get angry about players not knowing brand new fights. I joined a Midas7 group on patch day and there was a healer who quit because people were new. On patch day. People like that are just going to give themselves heart attacks they are wound so tightly. Personally, I love going into content and learning the fight first hand. Getting scared by mechanics and then learning how to deal with them.