I'm going to bring up something I do every time a conversation goes in that direction. Though some people don't accept the distinction, there's a pretty large gap between "Trusting a GM's intentions" and "Trusting a GM's judgment". Playing with someone who you don't trust the intentions of is probably a mistake. On the other hand, lots of people don't have 100% trust for a GM's judgement all the time (I'm one of them). So I'm going to suggest that "playing with DMs not up to the level they want their DM to be" is sometimes a given, because they don't expect that to be, in practice, possible.