This is simply not true. You cannot increase your simple reflex speed or your visual acuity by trying harder any more than you can increase your height.
You can increase your reaction time to complex situations and inputs by practice to bring it closer to your simple reflex speed. And of course, having good reflexes does not mean you have a good reaction time to actual events needed for a task.
The idea that you can improve your vision by trying harder is, of course, absurd. If true, the entire profession of optometry would be turned upside down, the vision correction industry would vanish to be replaced by a vision coaching industry.
Absolutely. Having innate abilities doesn’t make you a pro at something. Having a genetic predisposition to leanness and muscle gain doesn’t give you an athletic body – you still have to actually get out and exercise. Having good reflexes, visual acuity, or hand-eye coordination doesn’t make you able to expertly intercept a pass or land a cross-court basket without actually practicing.
Your entire attitude is like that of people who tell dyslexics they just need to practice reading more, depressed people they need to snap out of it, manic individuals that they need to calm down, adhd individuals that they need concentrate.
Not everyone has equal abilities. That inequality doesn’t start or stop with the diagnosis of a ‘disorder’, there is a whole spectrum of inherent abilities.
Of course, you should not use this as an excuse for not putting in the effort. Most people can become reasonably competent at most things if they study and practice regularly. They may need to work twice as hard to get there, but they will get there if they persevere.
Personally, I’m absolutely terrible at memorizing. Yet, I still learned Japanese well enough to be able to read books and watch shows. It took me over ten years, when other people do it in less than five, but still. Of course, once you get past the beginning stages rote memorization isn’t the most important thing anyway. On the other hand, I’m never going to be a U.N. interpreter … there simply isn’t enough time for someone with my abilities to learn 7 languages fluently enough to do simultaneous interpreting with them. Life is literally too short compared to my learning rate.
Similarly, I hope to make it to plat or so in Overwatch someday, but making it to GM is not really realistic, never mind pro. (I’m already much too old to go pro anyway, and apparently age is the one physical limitation you’ll recognize for some reason).