I have an heuristic I follow whenever content I do not want appears on my FYP. I immediately scroll. I don't let the video get 10 seconds in, I absolutely do not let it finish. I do not swipe left to see other videos by the same creator. I do not click on the comments to see what other people are saying about the content. The second I realize I do not want content like that I swipe it away. If I get a series of such content I close the app and don't open until the next day. This has been 100% successful in removing unwanted content categories from my feed.

Alternatively, the opposite behavior is extremely effective in getting more content related to the current video. I let the video play all the way through or even play multiple times. I swipe left to see other content by the same creator and maybe watch a few of their other videos. I read the comments to see what other people are saying about the video.

It's pretty obvious if you think about it.