1700 articles is a huge amount, honestly.
the gambling part caught my attention since that’s closer to the kind of work I do. I am curious what actually went wrong there. Did the platforms reject the niche completely, or did the content get indexed and rank but just not convert as well as your other niches? Those are two very different problems.
Also, with networks like clickbank, CJ, and digistore, you can probably get away with more general parasite platforms since the content itself isn’t always flagged. gambling is different though. It gets a lot more platform level filtering, and some parasite platforms won’t allow it at all, no matter how good the article is.