I've been a guitar teacher for about 20 years, and my experience disagrees with your feeling. Some people have much more aptitude for the guitar than others; I'

I've been a guitar teacher for about 20 years, and my experience disagrees with your feeling. Some people have much more aptitude for the guitar than others; I've had some kids who have picked up playing chords in a tiny fraction of the time that is typical. While generally the ability to learn seems to correlate with their general intelligence level, there have been some who are far better than you would expect. This is not to say that practice isn't the most reliable way to achieve gains (it is!), but some 'just get it' and have ability (either musical or dextrous) on the instrument that most take a lot longer to achieve.