If you weren't aware, YouTube kind of has a version of this signal, which is to go into your history and remove the video you just watched. Supposedly this removes its influence on further recommendations. And then if that video or one like it appears again in recommendations, you can tap the ... next to the video and suppress recommendations for it by picking 'not interested'.

In my experience at least cultivating recommendations this way has worked really well for me on YT, I get consistently recommended a mix of stuff I want to watch and stuff that is at least theoretically interesting to me even if I don't want to watch it.

I wish other social services had the same mechanism (and wish it was more ergonomic on YT).

If I reached the video from the recommendations on another video/the YT homepage, I'll go back and select "Not interested" there. It's not foolproof, especially b/c the back button will still cause YouTube to update the original page (and so the previous recommendation can disappear entirely), but anecdotally this strategy seems to work pretty well.