Nigga Retroarch is a frontend, and people just use it for its features, which work on top of the emulation, such a shaders, overlays, inputs, savestate management and all the fancy shit, it mostly saves you the work of handling a bunch of emulators and just use one huge monolith of an UI for everything.
Honestly if these features were available on the standalone emulators i'd ditch them head on into the recycle bin. Because these guys are thinking themselves the saviors of emulation when in reality it's just what i said before, nothing but a fancy overlay to the emulation.