FLOSS used to include the ability to build software. Perhaps that's not important anymore but now a days some developers don't attend problems with their build recipes because they only consider what they release through binaries, whether on flatpak or whatever other binary repository they like. At least I dislike that, it's ok to me some or most users would prefer to grab a bloated binary rather than building anything, but that doesn't mean forgetting about those actually wanting to build from source, or wanting to use shared libraries and software from their distros, actually that's a requirement for free/libre software repositories. Not sure if the tendency is to move the gnu+linux users into app stores like the ones on windows, now ubuntu snaps, android play store and the like. Sure there's more security with sandboxing, but nothing one can't get with firejail, and if wanting MAC as well then firejail + apparmor for example.

At any rate, just my little rant. And if you're wondering, I use AUR on Artix, and I really hope I won't have a need for a flatpak stuff.