>>13804570
As is explained by OP's video (which is good, because I was curious about this), the ESRB rating is NOT legally required in any way. Indie game developers are free to make and sell their games in any way they want without having to give a single shekel to the ESRB, and many do (through their own websites, or other services like DLsite.)
However, if you want to get into the "big time" and be sold in EB Games or other such retail stores, an ESRB rating is required. Not because of law, but because of the store's policies - which probably isn't so much a corrupt deal between them and the ESRB so much as it is the stores want someone else to take the liability over age ratings, and the ESRB are the only ones offering that service.
TLDR - this screws small publishers not because an ESRB rating is legally required (it isn't), but because EB/Gamestop and Steam demand one.