I would say it's not so much overrated as it is that most people don't read theory and don't spend enough time practicing to develop mastery. Sex is like any other skill - you need lots of practice and experimentation to get really good at it. You've got to read theory and keep up with the current literature. You've got to consult with experts who are bringing forth new innovations.

In my experience most people are just kind of there and have never really put any thought in to getting good at sex, and that leads to a lot of mediocre sex.