I think the very unhealthy dominance of Facebook will only start to properly recede when countries outside the USA start to block its use. This is a highly predatory company that takes away sovereignty in each nation's cyberspace and it really only makes sense for foreign countries to block it and either let their own national corporate replacements emerge (as China has done) or foster the use of open social networks…
Small countries can ban facebook from doing certain things. Ultimately, some sovereignty exists even in global commerce. If New Zealand made (eg) political advertising, targeted advertising, or such ilegal, Facebook would stop doing it in New Zealand. That is treating the symptom, but it is not totally ineffective. Treating the problem is dealing with the monopoly. The current state of antitrust laws, norms and regul…
This isn't as problematic as you suggest. We don't need an act of Congress to deal with FAAMG.
The way the laws are enforced and interpreted has changed in a very meaningful way. Read the A&P cases and ask yourself, "if Congress hasn't changed the law then what's up with Walmart?"[1]
The DOJ Antitrust division is asleep at the switch. There are a lot of reasons for this. One reason is the Microsoft case. The DOJ won at trial big time. At trial they won a break up. This was scaled back enormously on appeal, and it damaged the careers of the very talented lawyers involved. This created a high degree of risk aversion in careerist antitrust litigators. Something similar happened after Enron (fancy people were upset by how vigorously the DOJ pursued members of their class), which partially explains the lack of prosecutions after the 2008 financial crisis.
There was also a sea-change in ideology coming from the law and economics movement, and from the re-framing of antitrust through the "consumer welfare" lens.
In practice, "consumer welfare tests" only consider price. They do not consider quality. To "consumer welfare" tests, a $50 phone plan that sells my location without my consent is superior to a $55 phone plan that does not
[1] https://www.nytimes.com/1949/02/25/archives/a-p-loses-appeal...