For the main systems it works pretty well. Where you start running into problems is on the older systems, and especially ones that aren’t officially supported by the scraper.
If you are willing to babysit it though, you can actually scrape some of the older and lesser known systems. I wouldn’t recommend it for more than around 100 games, since picking the art manually is a real pain. I have managed to scrape a decent amount of art that way for TRS-80 though.
I’m probably crazy for doing this, but for a handful of systems, I’ve manually created the gamelists and added the art; virtual boy, C-128, commodore PET, a prboom section I added, and retropie config scripts. ;P Any scraper is better than that. lol
^^ my other hobby