This is the incredibly profitable contradiction Facebook lives in.

They do everything they can to become the central place for online communication and profit enormously from that. But they reject any of the responsibility that ought to come along with that, the refrain being what you're saying here: "well, you can always just go somewhere else"

Except that when online communication is as deeply siloed as it is it's extremely difficult to set up an alternative. How will people even find out about it when their entire online lives are lived on Facebook? This capture is exactly what Meta wants. Remember internet.org?

https://en.wikipedia.org/wiki/Internet.org

Picking and choosing which services people can use is Zuckerberg's explicit goal.