Sandboxing is nice, but is not exclusive to Flatpak. I’m talking about the software distribution model.
Distro maintainers also ship software with bad defaults. I want to be able to easily control that.
So you trade distro packages which you can usually customize pretty well if you need to (e.g. modified Arch packages on the AUR) for Flatpaks where you have no chance at all to do that because the package build script isn’t available? And the problem still isn’t solved because now the people who can set bad defaults still exist, they’re just different people.