You queued up for a dungeon and got matched with Trab Godslayer, and you start the dungeon to discover that he is wildly misnamed. Trab Godslayer is probably not slaying gods. He’s definitely not slaying the monsters in this dungeon. One wonders if he could manage slaying a mosquito. The point here is that Trab is a detriment to your party, and that’s going to be a problem as you go through the entire dungeon with Trab.
So what do you do? You obviously have a bunch of options here. You could, for example, stop the run and explain to Trab that he needs to step up his game, which might help you out or might actually cause the whole run to devolve into a nasty argument. You could just ignore it and carry Trab during the run, which might be annoying but will avoid any fight. You could offer to help Trab understand things, offer extra explanations, or so on. There are a lot of choices. The question is, which one is your choice? How do you handle bad players in MMO group content?