Backgrounds are fully customizable in 5e, RAW.I would rather they get rid of the "fully customizable" aspect. Backgrounds were great; turning them into just a free selection of some stuff is a big retrograde step, IMO.
(That said, I would definitely remove the ASIs from backgrounds before removing customization - by preference I'd just build them into the ability score generation step, but if they must be kept separate then make them genuinely separate. That is, they're not part of race or class or background.)

Player's Handbook
Everything a player needs to create heroic characters for Dungeons & Dragons the world’s greatest roleplaying game.

There isn't anything in there that says this is an optional rule, and the only thing you're advised to work with your DM on is the Feature.