The EU, rather famously, managed with Microsoft. It's mostly the US that's beholden to large corporations over people, rather than it being an intractible problem.
> Meta hardly has anything approaching a monopoly for either advertisers or consumers
Meta does not command the lions share of the time spent on social media, but claiming >20% of revenue is oligopoly territory [0,1]
> Consumers frequently post pictures on X, LinkedIn, Google Photos, Strava, Snapchat
Do you really belive LinkedIn and Google Photos compete with SnapChat and Facebook for "Sharing photos with friends on social media"? If so, you might as well throw Flikr and Imgur on your list, though I wouldn't count them in the same market either.
[0] https://www.emarketer.com/content/meta-s-ad-revenue-share-va...
[1] https://www.statista.com/statistics/242549/digital-ad-market...
Microsoft keeps deleting ways to install Windows without signing up for a Microsoft account.
Twice in my life I've created a Microsoft account to do something that required a Microsoft account, and then a few days later they demanded my phone number. Because they know perfectly well that if you demand a phone number during signup, it deters more people from signing up, but if you demand it after they've already started using their account, they're less likely to be willing to throw away the account. I was, though.
For some reason they haven't yet done that with my Minecraft-migrated account. Or did they? Maybe I entered my phone number there and forgot I did so.
Also, if real competition arises, it's just bought and merged (Facebook buying instagram) since anti-trust laws have not been properly applied, especially in the digital sector.