You might be interested in this here https://github.com/itchio . But I do not think Itch is looking for developers and the site itself is not open source.
I suspect the people that are highly interested in exclusion filters do have ways to cope with the current system. Single exclusion is possible with a bookmark for a favorite search.
Multiple exclusion is just not as usefull as it sounds. Client side, one can simulate it quite fully with the tampermonkey script I made a while ago. It can hide items and or developer's items. So just visit every tag you wanna exclude, hold the hotkey for hiding till a lot of the popular games are hidden. Rinse, repeat. A better approach is to just search what you wanna search and hide individual games. Since they stay hidden, they will not bother you again, when you search similar games. Also usefull to hide the stuff you already know.
Tags are unreliable to begin with and I suspect most people do not browse for games as they would enter a complex database query. While Steam has this feature, I did not even know about it. And there the tags are a lot more reliable and from a small fixed pool of tags.
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How would data entered by the developer be of any significance about the quality of the game? Web development and publishing a game might be related to game development, but it is different skills.
What kind of data are you talking about? Is it somethign from here? https://itch.io/directory