Despite being poorly implemented by platforms nearly 20% of kids have stopped, and so soon after the laws were enacted? This seems to have worked better than expected. A few fines in the direction of Facebook and Google will improve these numbers further.
Then you just need to wait. When smoking was banned for under 18s the day after they still smoked as well. These days smoking is rare. The current generation is a lost cause, they'll VPN their phone addicted brains to get their daily fix of TikTok if they need to (my niece in Australia is the type of person who would watch two twitch streams in parallel and then have a mild panic when someone asks her to put the phone away at the dinner table, it's insane).
The next generation now stands a chance. People are less likely to join social media as a new customer if they need to jump through hoops to do so.