If you are really curious about the development of skill you can pick up the book Talent is Overrated. The general idea is that there is a difference between practice and deliberate practice. The 10,000 hour rule and putting in time do not paint the full picture, after all, most people work 45 hours a week for 30+ years and never really get any better at what they do.
An example from the book was that as a general rule, the more experience an auditor or a doctor has, the less likely they are to detect corporate fraud (auditor) and the less knowledgeable they become about basic anatomy and diseases (doctor). Simply spending time doing something is not enough to improve.
Spending time deliberately working on weak areas and tackling things that are not very fun to do is the primary difference between those that are okay at something and those that are great. There are outliers in the doctor/auditor example that get genuinely more skilled year after year, and the difference between the two groups is deliberate practice.
Obviously there are some limitations to this from a physical perspective (there will never be a 5' 0" quarterback in the NFL if all lineman are 6'+), but the general idea holds true for all realms of skill and efficacy.