Websites could easily add X-Recommended-Age or X-Content-Rating headers where browsers could enforce a decent set of filters for adult-oriented content.
Popular platforms, I think, have age ratings on streams (twitch stream age tags), youtube, etc
The above would cover 90% of content-related concerns and combined with things like cloudflare dns filtering you'd have a relatively safe internet experience.
The interacting-whith-people (or oddball harms like character.ai) concerns can then be more easily policed by parents.
The industry has chosen not to implement basic controls and is asking for government controls.