could we make a way to hide boards threads?

If it's by certain individuals which you don't want to see, then you can use the Forum Enhancer Kit (FEK), which is a third party app developed by one of our GD Wardens (Tundra Fizz) that provides many useful features like blacklisting, custom avatars, and vote count viewing. It recently underwent a change from an open-source browser script to an extension, so it's missing a lot of its old functionality, but it will be gradually recovering all of that as he has time to do so.

If it is not threads by specific people, then there's no such thing that exists to automatically decide if a post is a circlejerk and to hide it for you. You'll just have to spot them by the title and ignore them; maybe viewing the boards by Hot sorting would help you see more quality content (not guaranteed lmao).