My verdict: the marketplace to find the API you need.
RapidAPI is perfect for quick prototyping or specific needs. It's good and often cheap (lots of freemium), but reliability varies greatly from one API to another. You often have to dig a bit to find the really reliable vendors ('Verified'). It's a gold mine for quick prototyping or finding an API for a very specific need without reinventing the wheel.
What I like less: the very uneven quality between providers. Some APIs are excellent, others are scams. You really need to check reviews and test before committing for production.
My advice: use RapidAPI for prototyping or occasional needs. Filter by "Verified" and look at reviews. For critical production, thoroughly test reliability and support before committing. And always have a plan B.