If someone is saying they can't learn a skill they're manifestly capable of, then focusing on how they can likely do more than they think is the correct corrective to apply. However, everyone does have limits, and ignoring those limits and insisting that the same level of attainment is possible for everyone through effort is a toxic mindset which implicitly (or explicitly!) punishes people for being human as opposed to idealized automatons.
On the other hand, if someone is insisting that they can learn everything up to the highest levels and become a 21st Century Renaissance Genius, focusing the replies on how limited time is and how much there is to know is the proper corrective to apply. Apply that corrective too broadly and it's crab-bucket or tall-poppy mentality, and anti-intellectual bilge.
We do need to tear down the idea that people are inherently "good at" learned skills, however. That's never a proper corrective, it's always nonsense, and it devalues the hard work the successful people put in while demoralizing the people who wish to become successful in something.
I use to coach high school policy debate in a major metropolitan public high school and the level of "I can't do this, I'm just not good at this" that shows up the minute kids encounter difficulty/obstacles, and specifically in non-physical labor, is mind-blowing.
We tell children "anything is attainable if you put your mind to it" then turn around and imply to children through our actions, cause they're good at reading those, that some people have "it" and most don't, e.g. sequestering the smart kids into completely different tracks from the regular kids; math teachers demonstrating disappointment that a student doesn't understand something while praising the kid who grasps it much quicker.
What's striking to me is that social media, and specifically IG culture, has made strides in tearing at this contradiction in the domain of personal appearance, e.g. not only weight loss/fitness transformation but even the celebration of 'confidence is all you need' for women with more robust bodies. But in the final analysis, I find physical accomplishment in our culture to still be a distinct domain from mental accomplishment.