step 1: chose the Cores (emulators) for the consoles you want
step 2: scan the folder that has your Roms
step 3: start and play the games that are neatly sorted by consoles with fitting icons and everything
it is literally impossible to make it any easier and have less steps.
You are quite simply wrong. It is very possible to make it easier and have less steps.
Step 1 is entirely unnecessary. RetroArch is already able to determine what core a rom would require and could simply download it on-demand.
Or even come with all the "typical" ones (GB, NES, SNES, N64, etc.) by default, although I am not sure if that is actually possible license-wise.
Step 2 is obviously necessary.
Step 3 I already went into. The listing and filtering capabilities of RetroArch are really not very good. Once you reach the likes of thousands of entries, it becomes a chore.
Not that there is a better alternative out there, mind you. At least not to my knowledge.
There are, however, lots of programs dealing with hundreds or thousands of entries and offer way better filtering/sorting/etc. capabilities.
At some point the user needs to do something and know some basics. Its like you are looking from the perspective of someone who never used a computer before.
I am looking at it from the perspective of UX and UI development.
The goal of which should always be to reduce the hoops to jump through as much as anyhow possible (without restricting capabilities).
I can guarantee you a lot more people would be interested in better collections, but right now would only dare touch something like the SNES Mini.
And one reason for that is ease of setup/access/use.