People need to realize that before Flatpak, distributing a small-time Linux app was a nightmare. Appimages were your best option if you wanted to avoid distro specific builds, PPAs and AUR, etc. Ever since packaging 2009scape on Flathub I haven't looked back. It auto updates. People can find it from software centers. It works on all distros. It connects straight to upstream's CICD. It even forced us to adopt XDG compliance so we could sandbox it better.
Yes, Flatpak has downsides like the download size (on disk it doesn't matter because it gets compressed and the runtimes are shared, same as literally any other package manager). But overall, I hugely welcome it over the options we had before. Much love to the Flatpak and Flathub devs!