I had the opposite experience. I have been using EndeavourOS on my desktop since November, zero issues. This weekend I’ve been distro hopping on my old MacBook pro and almost every distro had a problem. Some didn’t boot, other had wifi issues, trackpad issues, keyboard volume keys not working, high CPU usage… EndeavourOS was the only one I tried that just worked out of the box with no issues
If I developed a Linux app I would absolutely package it as a flatpak. If a package is in pacman, however, I see no reason to use the flatpak version instead.