You bring up a point I have been giving a lot of thought lately.
Average age of Grandparents at passing: 89.5
Diet: Meat/fish/wild game heavy, with some vegetables and starches at every meal. Big breakfast, light lunch, moderate dinner. moderate to no alcohol intake some tobacco consumption during lifespan, either from smoking, working with tobacco (transdermal, from the sap on the plants), or being exposed to those.
That seems pretty successful to me.
I think if we follow the basic diet our successful ancestors did, then we follow that which our genetics is most likely set up for. Generations of DNA go into people who have been successful with those diets. and if the level of success is good or acceptable, why change the program?
Depending on ancestry, paleo-diets are not the same, determined by the resources available.
My Wife's people ate a lot of red meat (almost all wild game) fish, and fowl, and relatively low amounts of green vegetables, simply because such were not available. Tobacco use was common. Unfortunately, so was alcohol use, though not universal (she does not drink, either). Much depended on the food resources available, but longevity is dependent on so many other factors besides diet, it isn't funny.