I'll give flatpak and snap one thing: they did make some concession to avoiding duplication, unlike docker which utterly duplicates everything.
With flatpak and snap, applications can depend on/pull in a maintained external layer. So you might want 'gnome environment, version 43' and other applications that want that can all share. That layer can be updated independently of dependencies. You might have two instances of the gnome layers (say 43 and 44) due to different applications declaring different versions, but it's not too bad.
Now there is some duplication, some libraries that an app says "oh, no particular layer for this one, fine I'll just bundle it". But at least there's a mechanism to not necessarily do that for everything.
I'll give flatpak and snap one thing: they did make some concession to avoiding duplication, unlike docker which utterly duplicates everything.
With flatpak and snap, applications can depend on/pull in a maintained external layer. So you might want 'gnome environment, version 43' and other applications that want that can all share. That layer can be updated independently of dependencies. You might have two instances of the gnome layers (say 43 and 44) due to different applications declaring different versions, but it's not too bad.
Now there is some duplication, some libraries that an app says "oh, no particular layer for this one, fine I'll just bundle it". But at least there's a mechanism to not necessarily do that for everything.