the simplest way to explain it would be that the usability of something is directly connected with how happy the users would be when using that something, and how happy the users are determines whether the product is good enough in the long run
Take DeviantArt as an example, it was considered THE best G-rated art website a few years ago, and now a lot of users have stopped using the website and would rather stick to social media instead (DA users, I said "a lot", not "all". Don't reply with "Oh I'm still using DA"). Why did that happen? There was a change in UI that was sudden and changed almost everything that everyone had to relearn how to use the website, which is a BIG no in terms of website maintenance, and they didn't revert it at all, I think it's because they thought the users would be patient in learning everything again, which didn't happen, and now DA lost a lot of its users, but it still works as there are still some old users that stayed and new users that didn't have to go through that
Now how is that relevant to itchio? It's having a similar situation where a lot of people are complaining about the same topic, in this case, the tag exclusion feature, and in DeviantArt's case the sudden UI change. I know it's been a long time since we asked for it but we're still here, but I'm sure the active users of Itchio are reducing, I mean look at the recent games, all of them are either low effort, horror, visual novel or all of them, the only ones that can be rated as "good enough" is the occasional big projects and a few of the ones that won game jams, from what I see these two are the only things keeping Itchio alive.