whether the app is "free" enough for their liking (MIT vs GPL-based license, etc),
whether it picked the "right" frontend in the never-ending GTK vs QT battle,
whether it is written in an "acceptable" language (Electron being Satan Incarnate, of course),
whether it has been properly packaged as a DEB/RPM/Snap/Flatpak/AUR/AppImage, etc.
Fail any one of these things, and the app is instantly "unusable" and we should all use ncurses-based obscure-thing-I-found-over-the-weekend-in-some-dude's-PPA.
Meanwhile, an increasing array of "free as in freedom" apps that are widely available and cross-platform (e.g. Blender, VLC, Audacity, Calibre, etc.) serve the larger community by just letting people get shit done, and build up name-recognition as a result.