On which grounds would you punish some companies which are using a fully legal platform? If you had beef with the ad contents, you'd punish them already for that. But if you have beef with the platform algorithms, punish them for exactly that. Not over proxies! As long the algorithm was designed for creating dependence, than regulate that - exactly like you (should) regulate other substances creating dependence. And some countries are going exactly this way: not only Australia but also Finland, Spain...
Ok, imagine a law punishing a platform comes out. How will it be enforced? You can fine the companies but they can just close presence in europe. YouTube will continue to work even if all the YouTube's servers in europe are gone.
Or should the only outcome of the law be that the police could confiscate phones from kids? punish parents for allowing social media? Laws are not useless, at least teachers and parents will have a clear call to action. But still