Plain vegetables are not palatable because they have very little nutritional value, like saw dust. If you were as rewarded for eating vegetables as you are for foods with actual nutritional value you would quickly be malnourished. If you ate a vegetable only meal you wouldn't even absorb the fat soluble vitamins from them because they don't have any fat.
In the wild where the immediate pressure is on getting enough calories and macronutrients while lack of micronutrients only cause problems in the long term, any human wasting energy collecting and digesting food that doesn't have calories and macronutrients (vegetables) would be quickly weeded out.
Look at the nutritional information of any vegetable for yourself. Fruits, nuts, legumes, grains, potatoes etc all come with the fiber, vitamins and minerals that misinformed people think can only come from vegetables while also being loaded with calories, protein and essential fatty acids all which are pretty much completely lacking in vegetables.
I haven't seen any study suggesting eating vegetables is cancerous but have seen a few from meat and processed meat (studies from the WHO).
I'm not vegan, but meat is 30% of my diet. If vegetables are that bad in nutritional value, why can you survive being vegan and just taking vitamin B12 complements?
I think using palatability as a way of measuring nutritional quality is not going to help you in the context of a society raised on ultraprocessed foods, because sugar, salt and other chemicals give taste to food without giving it nutritional value.
If vegetables don't give you as many calories as meat and as you say: "...any human wasting energy collecting and digesting food that doesn't have calories and macronutrients (vegetables) would be quickly weeded out", why there are so many animals still alive after millions of years eating plants (some of them eating many kilograms every day)?
I think I didn't mention meat anywhere. I am actually vegan. There are a lot of plant foods that are relatively high in calories, vitamins, minerals, fat and protein which I mentioned: fruits, nuts, legumes, grains, potatoes, berries and so on. Vegetables (e.g. cabbage, lettuce, tomatoes, cucumber etc) only have vitamins and minerals when you consider that as human you don't have the digestive system and time to digest tens of kilograms of food in a day.
Sugar contains a lot of energy so it's not fooling you when it's tasting great.
Can you say which specific animal is alive eating food without much caloric content (and which specific vegetable are they eating)?
