where anyone can create and fully own unstoppable communities.

One man’s “unstoppable communities”, are another man’s “spam and NSFW content” 🤷

I think you need to make up your mind what you actually want. Gatekeeping access under the guise of fighting spam seems directly contradictory to the stated goal of your project, and assuming it wouldn’t be flooded with such content when most of the internet consists of such was pretty naive.