There’s a great video on Cracked about Idiocracy with almost a million views (so, there’s a chance you’ve seen it before). Go ahead and watch it, but the main message, as I see it, is that actually those people in the future are in a pretty good situation, because they acknowledge that they are stupid and they are ready to listen to someone who is more intelligent then themselves. In that world it doesn’t even take much to better everyone’s lives, but they still need to come together and listen to that one rational voice, and that’s something we’re clearly unable to do.
And this is the problem with morons. Even if they acknowledge that other people have more knowledge and are better educated, they often come up with excuses like downplaying “book learning”, referencing “school of hard knocks”, or relying religiously on sources such as the Bible or radical news outlets, depending on their background. They don’t understand contexts and everything is black or white.
Assuming the game is the usual sort of adventuring (which I tend to avoid these days), it’s fairly safe to assume the characters are confident (probably overly so), because otherwise they wouldn’t go out and face whatever obstacles they are going out to face. This probably means the stupid ones are also the ones, who are at least close to the model depicted on the video. The kind of people, who don’t know they are stupid and, due to their over-confidence, will assume they are right.
These kinds of people have a tendency to mess things up. They will boldly go into danger and thus drag others with them. This is probably what you should do from the point of view of realism. However, most fiction is not about realism. You will have fun sabotaging all the plans of the other players, but in the long run that joke will die a horrible death.
It’s like Trump. At some point his antics were fun. Not any longer. Now pretty much everything he says and does is just depressing. How long would you suffer someone playing that character in your group?
If you play stupid, keep it low-key. It’s just possible that your character does know there are better people in the group to handle the planning. Here’s the problem for me: I want to be part of those discussions. This is why I try not to play stupid characters. I like to contribute and not only by creating false feeling drama through being wilfully stupid.