Regulation is a useful tool when there is quantifiable harm to an involuntary third party. That is not the case here. People have an infinite amount of electronic communication tools and services from which to choose. These are all voluntary without negative externalities causing harm on individuals outside the conversation (or outside the site when relating to the cookie policy).
Network effects can be overcome locally, by talking with your contacts and getting them to move to a new app/communication mechanism. It takes time, but compelling arguments will win in the end.
I think one of the big missing pieces in your parent comment about choice and negative externalities has to do with this network effect and I do not think the argument that it can be overcome locally is a very compelling counter.
It certainly is a difficult thing to do, but we see it happen time and time again. TikTok is now the biggest app, and it was nowhere a few years ago. Same with things like Insta, What's app, Signal, etc.
It is definitely a hard thing to overcome but not impossible. Especially as people become more privacy focused. I, for example, have had zero luck moving my family to Signal, and I'm the only non iPhone in the family network with my grapheneos phone and receive constant complaints about how I mess up group threads.
