The problem would be that people want to avoid seeing some things, and they really want to avoid their kids seeing things.
So what if we define a group of flags that can be set to say "This content does contain X" or "This content does not contain X." If the flag is not set, we don't know. Then web filters can just block content that lacks a flag saying "This content does not contain X."
If I post your real name, address and bank account credentials online, or photos of you in the bathroom, or start a forum to plan acts of genocide against your race or religion, or maybe spread plausible slander about you on every social media platform I can, that's perfectly acceptable under your terms. But it doesn't help you if all you're allowed to do is set a filter flag on it. It's still there, having an effect.
The web isn't just teenage edgelords shitposting at each other for lulz anymore, there are actual real world consequences at play.
[edit] adding here that "Intentional Infliction of Emotional Distress" is a real thing in US law. so, legal remedies do exist.
https://www.findlaw.com/injury/torts-and-personal-injuries/i...