If you sort through games on pc and are willing to use a browser extension, there is another solution available. You would simply hover your mouse over a game and press a button to mark it as seen. The idea came about here https://itch.io/t/3477347/add-an-option-to-exclude-owned-games-when-searching and in some other threads. You can also mark developers. The actual "marking" is just css that will hide or highlight the games.
But if you really want to check out all games in a tag combination, the bookmarking and reverse recent order will be shareable between mobile and pc and should catch all games.
A "negative" collection for browsing sure would be nice. Steam has an ignore feature for games. But I actually do not know, if it is designed to hold hundreds and thousands of games. Itch collectons are not even designed with thousands of items in mind. So I guess, server side filtering of the general browse feature is just not a very practical thing to do. Maybe for a special page like recommendations.