In my generation and upbringing in a culture, where end-stage capitalism grass roots propaganda promised you great fortunes if you were only to apply yourself, few things were taken as granted as the ten thousand hours rule: To achieve excellency, you need to spend ten thousand hours with deliberate practice. Not only is there a minimal amount of effort you need to put into getting good, but the rule is an actual operationalization of deliberate practice: to git gud, practice is the main determining factor.
Contrast this with the following quote from Dan John about great athletes:
Tommy Kono, the Olympic lifter, was world class in two years (basically) after first touching the barbell. John Powell, the discus thrower, believes that one should be world class within THREE years of focusing on one thing…otherwise you are just not good enough.
Now, one could argue that the sport at the time did not really perform at the same level as it did today, so it was relatively easier to get to the top. Which is certainly true for some sports, but in strength based sports with some drug control, this does not seem to be the case.
Furthermore we can observe this with any new generation of young athletes; the people that end up at the top usually percolate there very quickly, regardless of the quality of their training.
Not only is the 10k hour rule a busted myth, it is REALLY busted when it comes to the top of the crop:
Overall, deliberate practice accounted for 18% of the variance in sports performance. However, the contribution differed depending on skill level. Most important, deliberate practice accounted for only 1% of the variance in performance among elite-level performance. 
The same also holds for non-athletic efforts, and indeed, Macnamara and Maitra did try to replicate the infamous violin study which started this whole thing, only to find that it does not replicate. 
This definitely does not invalidate the value of deliberate practice. It is integral to getting better, and in general we tend to underestimate how much better we can become by only a little practice, or, to be more honest, how much we suck without practice.
Also I suspect when you put in ten thousand hours of deliberate practice into something, it would classify as mastery by most standards. But you might still be far away from world class, or even the national top.
Or to put it in catchy phrases: Hard work beats talent, if talent does not work. But talent does not need to work that much to beat your ass.
|Macnamara, Moraeu, Hambrick - The Relationship Between Deliberate Practice and Performance in Sports: A Meta-Analysis, paywalled by bloodsuckers https://journals.sagepub.com/doi/10.1177/1745691616635591
|Macnamara, Maitra - The role of deliberate practice: revisiting Ericsson, Krampe, Tesch-Römer (1993), https://royalsocietypublishing.org/doi/10.1098/rsos.190327