Comment by anonymars
The missing ingredient is usually "competition"
Same thing with the "private sector is always better" religion - if there's no meaningful competition, you end up no choice coupled with a profit motive, vs. no choice but I can at least nominally vote and be represented
ISPs are usually a good example in the US. My old apartment had one provider, and wouldn't you know it, at my new apartment with multiple providers, I got five times the bandwidth for half the price.
See also: enshittification
In light of competition being the missing ingredient, the question becomes how does one maintain ongoing competition in a system where the bigger of two competitors tends to win and the winner of two competitors tends to get bigger? That's exactly what happened here: Facebook was bigger than WhatsApp, and FB+WA is bigger than Insta, so FB+WA+Insta is a lot bigger than anyone else.
Back in the day when Microsoft was the one in the DoJ's sights someone compared it to a dog race. Dogs don't have jockeys, so you have to figure out some other way to induce them to run. The way most tracks (probably all, idk much about dog racing but it's a useful metaphor here) do that is by having a mechanical bunny that runs out ahead of the dogs and activates their prey drive. The bunny has to be ahead of the dogs, but not so far ahead that they don't think they can catch it and give up. That means that every once in a while a dog will get the timing just right, go extra hard, and actually catch the bunny. At that point, the race is over for everyone until someone steps in to shake the dog loose from the bunny and give everyone a reason to run again. Our system is like that: we have to encourage everyone to do everything they can to catch the bunny but also ensure that they never actually do. Bill Gates was the first person in my memory to catch the bunny, and needed to be shaken loose. Now it's Zuckerberg, and probably Google, that need to be pried off of their respective bunnies so that everyone else has something to chase.