Fitness can be seen as a phenotype trait, i.e. the kind of phenotype that will produce the most offspring. Of course that is dependent on the environment, but it is worth noting that the kind of adaptation you mentioned can also happen epigenetically or by other means. Basically organisms can have some adpatability built into their genotype.
I meant that our goals aren’t aligned with the evolutionary “goal” of maximizing the number of offspring anymore. We are still deeply driven by evolved instincts, but we should recognize them as needs that our biology requires to be satisfied in order to achieve happiness, rather than goals in themselves. Of course we are still part of the biosphere and subject to evolution, but that evolution isn’t significant on our timescale or meaningful (in the sense that by our criteria of good people, we won’t evolve to be better). If we want to improve as a species, we should focus on a different, memetic, kind of evolution, passing knowledge and ideas instead of genetic material.