Hypothetically we've weakened the selection pressure against those traits, but they still have some impact. A celiac who continues to eat gluten will not be at

Hypothetically we've weakened the selection pressure against those traits, but they still have some impact. A celiac who continues to eat gluten will not be at their best or healthiest. They will have an uphill battle in life compared to everyone else. A celiac who stops eating gluten might spend more on food than other people, minorly impacting their life. (Or, maybe they eat more vegetables than average, and thus being celiac becomes an advantage!?) On a massive population scale, they will on average have some fitness modifier, and their genes will still be selected for or against- just more slowly. Just think of more severe conditions. There are many once-fatal or severely-debilitating conditions where we've enabled people to survive and possibly even reproduce- but the deck is still heavily stacked against them, and they do not on average tend to have large families with lots of successful kids. So a once-fatal trait becomes less severe, but it's still selected against.