I don’t think you’ll get a very satisfying answer, to be honest. They’ll probably just direct you to a page with the general guidelines — but those are often outdated and not that helpful in cases like this.
I’ve faced a similar issue with indexing myself. Some games that were released long after mine got indexed quickly, even though many of them didn’t fully meet the quality guidelines. Meanwhile, I’m still waiting to be indexed.
I’m not sure if Itch.io was always like this, but lately, as developers, we’ve been left in a bit of uncertainty. They’re probably just too busy and struggling to keep up with everything.
I’ll be following this thread — I really hope your issue gets resolved soon.