I think any time they could be exposed to something is the time to educate them about it. If that was even younger, that would be fine. Even very basic sex education can be taught to very young children to help keep them safe from abuse. Not talking about things openly, using scientific vocabulary, is a big problem.
Parental controls are excellent to stop “accidental” discovery, but at some point they will seek stuff out, and proper education should exist before that point. If parents are too embarrassed? ashamed? to have that conversation, it falls to the school/state/etc.
Parents not using parental controls are in my mind the same ones who would have been similarly oblivious or negligent in the past, I don’t think the technology has anything to do with it, except statistically volume and ease of access increases necessity. I don’t think I would blame tech companies any more than magazine publishers.
They don’t call them Lucky Goldstar for nowt