From your watch history, delete videos that are too similar to the ones you don’t want to watch.
Use the triple dot menu under the video suggestion to tell them you’re not interested. Choosing a reason is not necessary, but you can pick one if it fits.
If you think you’re going to lose out on something by doing the above, add the video to a playlist first. Not the Watch Later list. Make a new one.
Check your previously made playlists for content you’ve forgotten about. This might only apply if you did step 3 at some point previously.
Hints for improving the algorithm:
From your watch history, delete videos that are too similar to the ones you don’t want to watch.
Use the triple dot menu under the video suggestion to tell them you’re not interested. Choosing a reason is not necessary, but you can pick one if it fits.
If you think you’re going to lose out on something by doing the above, add the video to a playlist first. Not the Watch Later list. Make a new one.
Check your previously made playlists for content you’ve forgotten about. This might only apply if you did step 3 at some point previously.