And how would we know which mutations are broadly beneficial or not? What if humans of a future earth or larger society have needs we couldn't imagine, like radiation resistance or anti-autoimmune protections?

Besides, sometimes there are trade offs with no clear winning picture. Sub-Saharan Africans with sickle cell syndrome are also more resistant to malaria. What's worse? What's more necessary? How do we know malaria won't be a bigger problem tomorrow?