The circular logic of "survival of the fittest" is wild sometimes.
Fit for what, exactly?
"Survival!"
Survival where? How? In what conditions?
"The natural world!"
What natural world? Is this "natural world" in the room with us right now?
No,
"the fittest" as we see today
don't survive because they're fit.
They survive because of the ways people in a society cooperate.
"Fitness" is just an accessory.
It's a fashion trend of vestigial muscle you can only build by wasting your time.
(or spending it on something you're passionate about, if I'm feeling nice)
Bodies wouldn't be so diverse if there was some objective kind of "fit"
and people wouldn't be so mad about the "unfit"
if we weren't just as able to survive.