> But you have to live under the wing of your distro mantainers, instead of installing whatever you want from any third party. Isn't Linux supposed to be about freedom?

You don't. Yes, but if you don't take advantage of the freedom, that's not freedom's fault.

> Yes, you can install software using tarballs, but it's not usable for 90% of users, and not because of the distribution model, but because of the lack of standardization in a good, easy to use application-installing API.

See Flatpak. Go look at what software is available at https://flathub.org/apps , but both GNOME and KDE have application managers that can install from Flatpak repos (configured to use Flathub by default), and possibly the distro's native package manager as well (via PackageKit).

Or you can also use AppImage files.