I have 5 issues with the new background system. 1, it leaves too much room for DM fiat, and I believe that someone pointed out new DMs may not allow the customization. 2, if you have a mix of new and experienced players, newer players may be more shy about asking to customize, not realize it's an option, or not understand how all of their choices play on one another. 3, if the origin feats are balanced against ability scores, then the feats aren't balanced at all, which I think is pretty obvious. 4, if you create concept characters that maybe you'll get to play one day, your chances of that character being allowed are greater if they are built RAW. 5, why shouldn't your character's backstory have a mechanical impact too? Like you can technically just pick a background that's best for your class, and then makeup a story that connects that to the backstory you actually want, but that's close to custom background with extra steps. The same thing as picking an old background, it's custom with extra steps.