We'll update the docs to make our dependency on vacuum / spectral clearer - fair feedback. We do more than this though, we also use LLMs to help us identify other issues and recommend fixes.
RateMyOpenAPI is really designed as a quick litmus test to help people get their OpenAPI doc (and thus their documentation) in a good shape quickly, vs the hassle of setting up of individual rules.
People find it quite helpful to quickly build a todolist of things to do with their OpenAPI doc to get it into a much better state.
Co-founder of Zuplo here - we actually created the service to help people get their docs into better shape (we use your OpenAPI to power the dev portal in Zuplo). We find that if folks have a high ratemyopenapi score their docs tend to be pretty good. We have no plans to charge for this service.
Thanks for the feedback, appreciate you taking the time to try it out and comment.