How can this possibly be enforced though?

We can encourage decentralized platforms and "Not your keys, not your coins" as much as a we want. But even after all the centralized exchange hacks, leaks, losses, scams, privacy invasion, KYC requirements, spying, surveillance, fractional reserve, accounts being locked, transactions being frozen, coins being seized and on and on, the number of people using such centralized services continues to grow. There will always be people who don't care about the decentralized nature of bitcoin and are just here to try to make profit, and will use any centralized platform which promises them unsustainable growth or returns. And there will always be people who despite the tens of thousands of users who have lost funds because of centralized platforms, will continue to use them to store their coins.

The only possible way to stop people using centralized platforms altogether would be to outright ban them, and regardless of whether or not you think such an outcome would be a good thing, we absolutely shouldn't be looking for more government regulation or laws regarding the bitcoin ecosystem.