If there is a community that has a mix of content you like, and content you don't like, you can make a post / reach out to the mods to set up something like that.
It would be harder to do on the instance level, and impossible across instances.
For your request specifically: It's very hard to define "politics" and so I would be against such a community rule. It would make a lot of unnecessary work for the mods and be annoying for users trying to post in a community they aren't familiar with.
Personally, if I was still seeing the content I don't like 85% of the time, I wouldn't be that much happier. I'd rather just block it and be done with it.