It seems like most of the top level responses are responding to the title and not the actual argument. The argument Dan is making is that you can easily get relatively good at most activities. This is because most of the people doing those activities aren't actively trying to get to get better. 95th percentile is probably not the best way to put it since there are tons of activities where nearly everyone is trying to…
In the article he's saying that a lot of people fail to improve because they're practicing wrong. Now that's probably a valid point, and it should have been his thesis. In fact, he probably considers it to be his thesis, but he muddied the waters by providing it with a debatable introduction and title.