It makes me happy that you are listening to your body, and that you respect the line of reasoning behind the paleo movement. It is very important to know where we come from.
Like you said what is healthy for one person, is toxic for another. Nomadic people in Asia would survive on milk, and those that could digest it best would survive and thrive. So after many generations those there are tribes full of people who can digest milk. By the same logic if your ancestry was full of hunters and gatherers... a diet of mostly meat and veggies could would work very well.
Many fruits and veggies were seasonal. I would suggest that those who descend from northern climates do well on meat. So between the first frost, and sometime in spring/summer when foliage was ready... many people were subsiding primarily on meat. Those who could not handle it would perish, and those that could would survive, leading to populations that do well on a diet primarily of meat. For example the inuit and people of siberia.
"as if some starving paleo man would pass by some ripe delicious fruit, sadly saying 'looks good but I can't eat that because it's not good for me" "
I agree with this statement, because I think that hunter gatherers would eat what ever would fill their bellies. So if they saw a bunch of berries, I am sure they would eat lots of berries. However I do question the fruit of today, and how much fruit we "should" be eating. Much of it is has been engineered to have a higher Sugar content. Eating Watermelon for a month when it is in season, rather than all year round may have some sound logic.
"Really, the hard-core paleos eat almost purely meat and vegetables, and then they want to teach that this is the perfect diet for man and everyone should eat that way, and that is just wrong. That is an extreme diet that may work for a very small percentage of humans but for all others will cause severe health impairments."
This I disagree with. There are a lot of people world wide who are thriving on the "hardcore paleo" diet. People with alzheimers, epilepsy, and other brain problems when they cut out the carbs are able to function again. There are many in the cross fit movement who thrive on a "hardcore paleo" diet. Again it is my opinion that our ancestry plays a large role in this, and a large part of the world population did live in freezing climates for much of the year.
If you look at migrating birds, what you will notice is that their organs will literally change based on the time of year. When they land at their feeding grounds their organs will be very large, and ready to consume large amounts of food. But when it becomes time to migrate again, their organs shrink and the protein from them goes into their muscles. This leads to a more efficient flight. It is not so much about what the birds want to eat, but about how the birds evolved to survive. So I imagine it is the same with nomadic hunter gatherers. Notice how many natives in north america easily get diabetes. Western foods have only been recently added to their diets, and they get sick on them.
There is a lot to diet/health that we do not know yet... so using broad strokes often leads to problems.