Dying is part of the dungeon experience, correct. Every one of us have died in dungeons many times I'm sure. However, is dying 20 times to the same boss because someone decides they don't 'feel' like moving out of stuff or attacking adds, is that part of the experience too? What part does it get acceptable to just move on? Or is every single player expected to spend their 90 minutes of play time to stick it out and die to the same boss over and over because of one player's incompetence?
I was new once like everyone else, and yeah I made mistakes like everyone else. Not to the extent of causing my group to waste 90 minutes of their time on a boss. I don't think it's elitist at all to ask players to give it their best and not to be lazy so everyone has a good duty finder experience. And if they are selfish and ignore your request, to save yourself some time by leaving.