I don't see anything wrong with a social media ban for teens in concept. In execution, it'll be difficult to do effectively though.

What I would like to see is changes to the tax code to disincentivize the social media business model and the advertising industry generally. For example...

1. Tax the crap out of advertising revenue on social media platforms

2. Stratify the ads and ban the existence of paid tiers which include advertising. If you pay for something, you don't see ads, period

3. Ban the use of trackers and fingerprinting on any paid service without explicit opt-in

4. Create a tort for data leaks that travels with any company which handled the data. If anyone in the chain leaks it, you can take an action against all of them, and the penalties are individually assessed

5. Ban the collection and sale of profiling data for anyone under 18

6. Ban the ad-supported tier for anyone under 18

This heavily disincentivizes algorithms generally and makes paid tiers more appealing, which is much easier for parents to control. The problem with social media and teens is that teens can even sign up in the first place. Make them use a credit card, and you suddenly have a much higher barrier to entry. If I tried to subscribe my parents to HBO as a kid, it wouldn't have worked, and this is why. It wasn't because the government banned 14 year olds from seeing HBO.