I don't particularly disagree, but rather I've viewed the AUR as having value in that you can change build options (for instance enabling/disabling features) that may not exist in pre-existing binary builds.
The distribution aspect of the AUR is useful given the various tooling/helper utilities around it, but I don't see it as more effective than flatpak if you're just using binaries that already exist. While the AUR is a bit more of a direct path, you don't have to worry about system level dependencies changing and breaking the binaries with flatpak (even if that does result in more disk usage as a side-effect).
The distribution aspect of the AUR is useful given the various tooling/helper utilities around it, but I don't see it as more effective than flatpak if you're just using binaries that already exist. While the AUR is a bit more of a direct path, you don't have to worry about system level dependencies changing and breaking the binaries with flatpak (even if that does result in more disk usage as a side-effect).