The following guidelines are not required for submission to Flathub, but are best practices we recommend and consider for curation and promotion. These guidelines are designed to help your app and Flathub itself appear in the best light to users—they may change over time based on developer and user feedback.
I do think that as a store it should have some guidelines on quality, but not of the application icon’s styling
People erroneously conflate modern and flat. Flat is used as a bogeyman.
Plenty of old icons are flat, and modern icons are moving away from flatness. The GNOME-y icon they showcase is clearly 3D, and multiple flat ones they show they state they disapprove of - 3/4 of these are flat and disapproved of.
Saying “ideally, app icons should give the impression that the app is actively maintained, not an abandoned mid-2000s project” doesn’t mean “make it flat or else”
People erroneously conflate modern and flat. Flat is used as a bogeyman.
Plenty of old icons are flat, and modern icons are moving away from flatness. The GNOME-y icon they showcase is clearly 3D, and multiple flat ones they show they state they disapprove of - 3/4 of these are flat and disapproved of.
Saying “ideally, app icons should give the impression that the app is actively maintained, not an abandoned mid-2000s project” doesn’t mean “make it flat or else”