As a former picky eater, part of it in my case was certainly that my rural family did not know how to make vegetables. They would be boiled with some salt or sugar, no exceptions. So I thought meat good, veggies bad.

Then I dated a vegetarian and learned not only about the different ways things can be prepared (roasted, steamed, fried, baked, grilled, etc) but also other veggies like asparagus, bean sprouts, bamboo, different types of mushrooms (I know they're fungus, but just play along with me), mock meats, straight up different types of food like Thai and Indian, and it was such an awakening. I do think picky eating is learned somewhat.