Ao3 was built on the fact the creator wanted to read incest. I’m not even joking. I get what you’re saying, and I say this as an aroace that reads nothing but fluff and found family, but “don’t like don’t read” is the foundation of ao3. If you try and force them to regulate against it, those people are still going to post incest and child p, they’re just not going to tag it anymore. Allowing them to properly tag it allows you to protect yourself from it