A lot of the time when you're running in the Duty Finder, you are getting people who are completing their dailies or are running something for the 100th time to get something for their relic. They want it done quickly and they want it done now, and they don't have the patience for someone who is new. I'm not saying everyone is like that, but as people get higher levels and fall into that grinding category, you'll meet more and more of them. My advice is to find a nice social guild to do your dungeons with. Most servers have an FC where they level together, or do their dailies together. It creates for a much more relaxed atmosphere.