The evolutionary perspective that holds post-menopausal women as a dead end is not a very well developed perspective.
Is it your ability to read or your ability to comprehend that is your problem? I repeat what I said, with emphasis:
A woman that hits menopause and doesn't have children is a dead end from an evolutionary perspective.
Try to catch the words you missed. Hint: They're in bold type.
a lack of Grandmas is a disadvantage for any human offspring.
If you hit menopause childless, you won't become a grandmother.
Even if you make a great grandmother figure for the kids of someone else, any mutations making you a slightly better grandmother than average won't have been passed on.
That doesn't mean they can't be useful - just like a cave or a fire can be useful. But they won't pass any genes on, so they don't contribute directly to evolution. Indirectly, those who can take advantage of resources, whether it's antelope droppings, internet or free babysitters have an advantage in passing their genes on. But not the genes of the barren lady, no. That's a dead end. Slightly less useful from an evolutionary point of view than a dog or a fruit tree - at least those might pass their genes on and evolve as your offspring does.