You can do that with your browser, if you use some extensions. Use a user style extension such as Stylus and add the style in the code below. Replace games with the game-assets suburl. Copy the asset creators you are not interested in between // and itch, just as their url shows. And you can replace display: none with opacity: 0.05 to merely tune them out.
@-moz-document url-prefix("https://itch.io/games") {
div.game_cell:has(a[href*="//ignore_a_publisher.itch"]) { display: none !important}
div.game_cell:has(a[href*="//ignore_a_publisher.itch"]) { display: none !important}
div.game_cell:has(a[href*="//ignore_a_publisher.itch"]) { display: none !important}
If you want to do that with a button press, I made a tool for that, but it is not released yet. Maybe add some feature requests. It is an unpacked chrome extension though. https://itch.io/t/3477347/add-an-option-to-exclude-owned-games-when-searching