We require applications, and most applications we get are extremely low effort and we don't approve them. If you have open registrations you'll be doing a lot of moderation for spam.
Run the software that scans images for CSAM. It's not perfect but it's something. If your instance freely hosts whatever without any oversight, word will spread and all of a sudden you're hosting all sorts of bad stuff. It's not technically illegal if you don't know about it, but I personally don't want anything to do with that.