Gattaca wasn't a depressing film.
In Gattaca, anyone could have the genetic enhancement done to their children, it wasn't an exclusive proceedure that only a certain group could have done. There may be issues with the poor not being able to afford it, but Vincent's parent didn't look like a well to do people, just an everyday working class family.
The only problem would be the holdouts, those not believing we should be messing with such things. Like the modern day Amish, they and their descendants will be left behind. But that will be because of a personal decision, not because of an enforced policy.