It's actually quite easy. If you watch something and you don't want more of it, delete it from your watch history. If it's particularly bad, you can block the channel entirely. I do this a lot for obvious AI slop content. Only subscribe to channels that are worth watching. Now my YouTube feed is almost too boring -- it's only showing me stuff in a pretty narrow set of interests and channels. I see very little outrage bait, celebrity news, "influencers," or politics.

And hide "Shorts" entirely. They will reappear after a few weeks, but you can hide them again.

Shorts aren't all bad. I feel like they've slowly drifted to regular-video length, and the major difference is just the tall aspect ratio.