There is already a shitty way to get all reviews/ratings from Itch. I will not explain how (so I don't get banned by angry devs,) but I will hint that https://itch.io/feed?filter=ratings is a feed of all ratings, and doesn't require you to be logged it. Have fun.
P.S. Anyone who can scrape reviews with the hint was going to figure this out anyway.
P.P.S. Guys, either restrict reviews to be "friends only" (or even "author only") or make a normal API - this is silly.