Interestingly I became aware of this post through an email from Itch themselves, lol! So I wonder if that's how they planned to do a workaround for the time being.
In any case, Aionaykonn below me I think is mentioning this post which I was about to do too: https://itch.io/t/5149036/reindexing-adult-nsfw-content
So don't panic. They made it so now things that don't accept payments like this visual novel can be reindexed if you toggle a thing in the pricing to say "no payments". From the sounds of the post, it reindexes stuff daily so it won't be immediate. But the sooner you toggle that on anything that qualifies, the sooner they show up again. (Spread the word. :P )
They also seem to be working on getting another payment processor that isn't trying to control what can be bought, so there is a decent chance that things on Itch will get back to normal sooner than later.
Viewing post in Update: OW is now deindexed. comments
This game already doesn't accept any payments... :(
This deindexing seems to be separate from the mass ones and instead likely due to the fact that the gamepage has a content warning for SA, which is still being restricted more strongly even though this game is not NSFW. I have reached out to itch about the potential of reindexing it but it will probably take me a while to hear back because they are swamped with people emailing.
Thank you though.