You're just talking about 'explorer.exe' being 5 mb? You're discounting the numerous DLLs which the explorer uses, or even other shared resources which are used system-wide.
And 55 MB for a native app is paltry. Even the 'Google' app on Android is 285 MB, the Gallery app of OnePlus is 70 MB.
And 55 MB for a native app is paltry. Even the 'Google' app on Android is 285 MB, the Gallery app of OnePlus is 70 MB.