It's no secret that I dislike Malcolm Gladwell's books in general. He's a journalist, and writes books people think are pop-science – but only a bad example of a pretty universally terrible genre. His podcast, where he codes like a journalist, is actually pretty delightful – but people thinking he's got some novel insight into how society functions is... extremely dangerous territory.
One of the things that has entered the intellectual water supply is his "10,000-Hour Rule", where he says that, to achieve world-class skill, you have to engage in 10,000 hours of deliberate, studied practice. Of course, as the Wiki entry will tell you, the author of his only scholarly source for this says he was misrepresenting their research. It's not hard to see why: the whole idea is structured so that it can't possibly be true.
Consider Chess. It's one of the prototypical examples of this kind of "10,000-Hour"-ish behavior. But how could we possibly know that in advance? I'm going to list a number of board games, and you have to select the subset of them that take 10,000 hours of deliberate practice to master: Tic-Tac-Toe, Nim, Dot and Boxes, Battleship, Mancala, Connect 4, Stratego, Othello, Mahjong, Chess, Shogi, Go. Consider that some of those games have computer players that dominate all human players, even those who have tens of thousands of hours of experience, and therefore should probably be correctly understood as taking an unknown but much larger amount of time to get world class.
The thing is, "ten thousand hours" describes both the inherent difficulty of a task and the wider world of competition around it. If no one else competes at something, you might be able to train up and do well over a weekend – I strongly suspect this is how many skills-based Guinness World Records are set. And some things like Tic-Tac-Toe are so simple that complete mastery can be achieved well before you hit 10,000 hours (really, before you hit a single hour), no matter how competitive other people are.
Of course, most tasks aren't competitive at all, really. There's no incentive to get much better than pretty good at most professional tasks, due to the structure of modern employment, and we should expect almost no one to have done so. Deliberate practice is all well and good, but choosing to either practice deliberately or just get the job done... has a tendency to shift focus away from skill-building, past a point. You'll bump into more diverse scenarios, and pick up more experience, but in an increasingly specialized world, we'd anticipate the breadth of experience that time gives you to narrow over generations.
At the end of the day, practice does help, obviously. And some ways of practicing totally suck, and shouldn't take up our time. But a focus on hours is distracting, and "world-class skill" isn't a cross-domain idea. The whole idea makes so little sense it couldn't possibly be true, and yet the idea hasn't gone away. It's still out there, being strange and misleading, despite nobody really sticking up for it.