The thing is, I like having a watch history and I like having suggestions based on it. If I watch something that I don't want affecting my suggestions, I'll delete it from the history after watching.
The things I watch on YouTube, I generally have zero interest in watching again, and if I really want to, then I'll find it in my history. What I really don't want is for something I've seen to be recommended at the end of a video (where there is no clear indication if you've seen before it or not) or polluting the sidebar of suggestions.
I'd also very much like suggestions to fall off the list if I don't watch them in a day or two. Sometimes suggested videos stick around for weeks. I don't want to click "don't recommend this channel" or "not interested", because I might want that channel's content recommended later, and I might be generally interested in the topic, but not enough to want to watch it now.
And while we're dreaming of features: let me disable shorts permanently. I refuse to support vertical aspect video (and based on the minuscule number of views the recommended-to-me shorts get, people interested in the sort of content I am agree).