That's been talked about often.
There's an undocumented feature to exclude 1 tag. https://itch.io/t/160014/can-i-use-exclusion-filters You can put it in a bookmark. And you need to be logged into your account for the feature to work.
In my experience, the tags are not accurate. Your favorite game might be tagged visual novel, even if you would disagree. I think it more helpful to "exclude" individual games. That way you can filter away not only games you have seen and deemed one of those vn you do not like, but also the games you already have played and still clutter your searches. https://itch.io/t/1018893/a-never-show-me-this-again-please-button