That sounds ridiculous until you realise that they already do it. They decide what to show in your timeline by looking over every post and matching what they think you'll engage with most. They know exactly when you're being a dick, what posts to show you to encourage or discourage that behavior, who to show your posts to, and so on. Adding a box to say "this post looks pretty bad, maybe take a break now" wouldn't be difficult. They don't want to do it because negative shitposts make them money.