But I see the same problems as with email, chat etc. You can selfhost almost everything. But too few people are doing it. You can use Linux as your Desktop and at least 4% are doing it. Still too few if you ask me.

The system is explicitly setup so that normal people don't need to set up anything. Experts and enthusiasts are the one doing the complex work, while normies just use a simply client like this and power users can also use more advanced clients.

And if most of the people keep using the commercial and closed source options over the self hosted one, then I see this concentration of power.

That's up to all of us to counter by promoting the good solutions instead, not of just despairing and begging politicians to fix this (they won't, they'll promote monopolies instead)