One of the basis of comedy is an extremely absurd situation, something Joel is really good at creating due to his ADHD/autism.
To me, the issue with Joel is that he's really funny or really boring, no in-between and it depends largely on how much stupid you are willing to take on at the moment. For example, his bits are for the most part stupid as shit but, if he does them quick enough and move on, it's fine, but when he does a bit 80 times in a row for two hours straight, regardless of how funny it was at first, it's just fucking retarded.
TL;DR Joel is the fast food of streaming, sometimes you just want something shitty because it tastes fine and kinda familiar but just not too much to get fucking sick of it.