...and people can't take it when people don't know how the mechanics works.
This is how every raid has been and I don't blame these people. Considering I've spent 20+ hours doing the raid the first time, I rather get people and knock it out in three or less than train a bunch of new people.
People aren't going to be well oiled machines when you go onto Fireteams or some LFG site.
No, but you don't need to be Slayerrage or something to beat a raid either. Like if I got invited to do the Pleasure Gardens section, I could probably help any team at the proper power level beat it in three tries. Less if they're good/high and we can one phase it. Likewise, I've gotten a lot of people like that and beat the raid nearly flawlessly.
They are going to need a chance to learn how things work, they will stumble for a bit, and they will learn how to work the mechanics. It will take a while, but it will get done and everyone will be a better player from the experience.
Well, in my honest opinion, the people who did it first are likely more experienced than someone who did it five times six months from now, since they failed so many times. Going back to the dogs, I failed that for so long that I know tons of mechanics and tricks to make it stupidly easy. I can teach people, just like people can watch a video to get it down, but doing it 30+ times is what makes you good at it.
tl;dr(srsly?) don be a bish and give people a chance on LFG Raid Groups
Question, what about having experience means I am obligated to help others? I get why people don't want to see so many people excluded, but it is so frustrating that some people say I'm not entitled to do this or that, but said people are entitled to tell me how to enjoy the game.
Regardless of whether I help people or not, someone will or they will find other people no one wants. Either or, they will also get it done. The big thing is, don't tell others they need to share, just be the change. You'll make the game better by helping as many people as possible, over telling people, who you know absolutely nothing about, that they're awful for doing something you don't like, regardless of factors like time, personality, actual skill and so forth.