What does "might" mean in this context? Nobody showed up with a gun to force people to make a Facebook account.

It is, at worst, "popularity makes right." Which, to be clear: there are philosophies that take significant umbrage with that (there's a reason the US government isn't a strict popular vote for every position).

But the complaint seems to boil down to "I want people to go do something else because... I know they should." Not exactly compelling. People know themselves better than strangers do.

This isn't a claim that might makes right. It's a challenge to replace theory of how people want to engage with the world with practice. I suspect (because we keep seeing the same patterns over and over) that a replacement for Facebook is going to either not catch on like Facebook did or is going to find the need for heavy-handed moderation at some point in the not-too-distant future.

The idea of political manipulation and/or censorship on social media only became a thing after 2016, and even then it took time to ramp up.

All of the incumbents were established with network effects long before then, they are very sticky and unaccountable. Not Ma Bell level of natural monopoly but the network effects are pretty strong.

Look at Twitter under Musk, your standard beltway liberal type still uses it even though they hate him.

"Network effects" are a cheap excuse for people to not put their money where their mouths are.

I don't personally have a lot of respect for the people still using Twitter. I deleted my account before Musk bought them when they responded to a notorious TOS violator being elected President by changing their TOS.

All we have to do to hold the incumbents accountable is log off their service and log on to another one. Nearly 100% of the power in this situation is in the hands of the users.