There was an app that dealt with desktop entry and auto-update but it hasn’t bee updated since a few years already.
no repo (= virus danger)
Can be remedied with an official store/ being distrubuted by the devs themselves instead of random people. Appimage isn’t getting a tenth of the support flatpak is getting.
no deduplication of libraries
Might worth it if you have dozens of very heavy apps but it’s totally not the case if you only need a few simple programs.