For me it's a neuropsychological issue, not a digestive one.

I "can't" eat most fruits and vegetables because they trigger my gag reflex so hard I can't swallow them. After years of working with a dietician and a therapist, I've managed to get to the point where there are a few things I can eat that aren't meat, bread, or ultra processed trash, but it's hard.

Also: to be clear, I have just as much or more disdain for any other voluntary dietary restrictions. Kosher and Halal get the same side eye from me, having lived to middle age with both the constant side-eye from people who like to rag on "picky eaters" and the constant struggle of trying to find something to eat when out with friends, I view anyone who limits their eating options just because they can and they think there's any kind of morality to what you eat as a person throwing away the massive gift of being able to just eat.