This has been a long requested feature: https://github.com/itchio/itch.io/issues/738
Which, very unfortunately, is still not implemented.
I feel like this is one of itch's biggest problems, at the moment, and will probably deter many users.
No matter what kinds of games you like or don't like, as soon as you browse games you'll be plastered with genres you have no interest in. So at the very least, there should be an easy way to exclude genres (and other identifiers if desired) for good.