Composition over inheritance has become a meme that people repeat without understanding. Both have their uses, but if composition is all you use, then you're using a hammer on everything. There is no silver bullet in life and most undeniably not in programming.
Also, electron has a reason for existing. If it didn't have a use, it wouldn't have the number of users it has. You can't tell me in all seriousness that Qt, Gtk, Swing, Tkinter is easier to use than electron for the common developer.