Well, it did work so well with all the porn sites back in the 90s, didn’t it? Yep, that was sarcasm. Heavy, pendulous sarcasm.
Might work if you made it illegal for porn companies to have anyone under 21 on their site and ban the terms, “barely legal” or having the word “teen” in any of their categories or searches. Separating adult from teen and keeping sexual subjects only adult will help keep kids safer from pervert men who go after underage girls.