Never thought about it but banning non personal accounts sounds like a good start. I doubt such social media would gain any meaningful popularity though.
It's not, that's why people want a regulatory body to do it. The only way to get people to use such a system would be to regulate the current ones out of existence.
Banning them is a bit harsh and unrealistic, as they allow the platform to be monetized.
Here's my random idea: all commercial accounts must be labeled as such, and people should be able to opt-out from seeing any post by such accounts - except ads because, as I said, not allowing a platform to monetize is unrealistic.
I think legislating what is good and bad math is going to be exceptionally difficult.