I think that calling Gladwell's suggestion that 10,000 hours is the magic number to become an expert bogus based on your single data point is a bit hasty. Gladwell didn't say that everybody who puts in 10,000 hours of band lessons becomes the Beatles. The way I interpreted the book was that the 10,000 hours of practice was simply a prerequisite to becoming the Beatles. There were numerous other factors outside of this practice time requirement that lifted the Beatles to fame. Many of those factors were luck-driven, including but not limited to inherent talent that they were born with.

In fact, my interpretation of Outliers was that being good is simply a prerequisite - the rest is heavily luck-driven even though nobody really likes to talk about it.