No one is arguing that we haven't evolved at all. But humanoids have been around for millions of years, and the 10,000 years since the advent of agriculture is a very small evolutionary time step. So the reasoning is more that we haven't evolved enough to fully digest grains without damage to our gut lining.
> Our hunter and gatherer ancestors were starving
You'd be surprised that a lot of hunter gatherers (HGs) were doing a lot better than that, according to anthropologists. One number cited in Robb Wolf's book is that HGs on average only worked on procuring food 10-15 hours a week, with the rest spent socializing, resting, etc.
> people on raw-only diets consistently lose weight, even if they eat a lot
Do you have any supporting evidence for this statement? Virtually all foods on the Paleo diet can be eaten raw (meat, seafood, fruits, vegetables, nuts), and are cooked more for taste than digestibility.