> It's really tough to apply anti-trust law to companies that aren't selling commodities.
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...