For example, on Discord, all your messages are scanned for such. On Cloudflare as well (for over 5 years).
For now it means they have no interest to remove such content unless coerced or affected by the public opinion.
This would destroy all content though, not just for minors.
Absurd, but it works, in North Korea (death penalty), Iran (death penalty), China (10 year prison), and also protects victims from rape, or "rape" under financial pressure.
The alternative is to let responsibility of the parents to install web filter to their kids, and let others live freely on the internet, without sharing their history or IDing them.
In reality, TikTok also has really traumatizing content, yet is engaging tons of kids and teenagers, and IDing won't solve that, but good parents can.
CP is an edge case but that's because it's almost impossible to make CP without abusing children and you could view CP as an incitement to violence -- as incitement to abuse children.
Parents should ultimately monitor what their kids do. I have a pi-hole that subscribes to lists with millions of porn domains, but I'm a technical person. Non-technical parents are helpless, and kids can easily access it at friends' houses etc. The industry has not empowered non-technical parents to do this, probably because there's a conflict of interest. Lots of parents would use such options to keep kids off social media, and like all addictive things social media wants to hook them early. (I think kids should be off social media too, but it's not quite as nuts as letting them watch fetish porn.)
Porn is different now too. It's worse in a way. Like everything else it's subjected to a pressure to get "edgier" to maximize engagement. So today's porn is loaded with simulated incest, simulated rape, extreme BDSM, etc., things that young children are not equipped to properly contextualize. (Some adults aren't either, but at least with adults you can say it's their fault not the porn's fault. The line cuts differently with children which is why children can't smoke, get tattoos, buy alcohol, get credit cards, etc.) If you want to see the consequence of young kids (mostly boys) being raised with unfettered porn access go visit any women-coded space on the Internet (like Reddit) and search for threads discussing why so many men want to choke their girlfriends. Where did this sudden choking fetish come from?
I just pushed this idea as a "solution" to see what others think, but I don't know. Again perhaps educating the parents about how to educate kids about the dangers of internet, and perhaps a web filter for kids.
This is actually one place where AI could be useful, to do dynamic local content classification (instead of a blocklist), especially if integrated directly in Android / iPhone.
Like https://support.apple.com/en-us/105121 but more dynamic.
Perhaps find a way to force Windows / Android / iOS to include such "firewall"/webfilter by default.
The "porn has been giving men violent sexual fantasies" line has existed since before I was born but it always ignores that they're the top fantasies among women too. Among my friend group the more common refrain is women who want to be choked but their boyfriends are uncomfortable doing it.