Less broken than ill explained. There are two search boxes and the one titled search does not search tags and arbitrarily cuts off results and weighs the results somehow; for instance you cannot find this game with the search term death.
But in these tag combinations there are only like 50-70 games (nsfw is less common)
https://itch.io/games/tag-nsfw/tag-ntr
https://itch.io/games/tag-adult/tag-ntr
For that matter ntr alone has only 90 games. Many devs do not know that they can tag anything. But fetishes are not tagged most of the time anyways.