The "kids don't like broccoli" has a scientific reason. Kids have a lot more receptors for aromas tasting bitter (10 to 15k different chemical compounds taste bitter to them) which reduce to 5k or less when growing up. So some types of food that adults can eat without problems because they lack the receptors have bitter and vile flavours for kids.
I always assumed this is also why adults love disgusting cheese (I do to a degree as well nowadays). We just lost our sense of taste and call it refined taste.
The "losing taste" is actually a beneficial thing. Most things that kids don't like are either risky (e.g. coffee) or difficult to digest (all kinds of cabbage), so it is good that kids don't like them. For adults being able to expand acceess to available foods helps feeding the horde in difficult times.
Plant breeders have also been busy reducing bitterness/tannins in various vegetables like brussel sprouts and canola oil, so things are in fact less bitter than 30 years ago.
Brussels Sprouts are another one... I don't think I had properly cooked Brussels sprouts until I was in my mid-to-late-20s, and they've become one of my favorite vegetables. They're so fucking good dude.
I'm mostly familiar with animal feed, where nutritional quality weighs quite heavy during selection. For human consumption I assume there are some base nutritional standards when applying to enter the market with a new breed, but might heavily depend on your region.