Calling simple myopia a disease feels like a push to get insurance companies to cover basic vision care, but calling half the human population "diseased" seems like standard medicalization creep.
Almost no myopia in hunter-gatherer populations. I don't view it as "disease" but it's not physiological state either.
I don't think you'd make it far as a hunter-gatherer if you had physiological myopia. Both of my parents are severely nearsighted (my dad around -4 or -5, my mom is worse than -8), and all of my siblings have myopia. It's definitely genetic too, but for less severe myopia, I think it's our environment.