Well I am not a fan of RapidAPI for a couple reasons, firstly them taking such a big cut of an API provider's business and secondly their marketplace feels kinda spammy and low quality.
I am trying to build so that there is little vendor lock-in (you can export your users to other auth providers, billing is integrated directly into your stripe account, etc) so that you still have the choice to migrate if you ever feel unhappy with the service
I think the biggest issue is that when an user makes a chargeback they don't pay you. Which makes the 20% cut they take a bit too much in my opinion.
Also the marketplace is getting full of people abusing free APIs for money.