Yes, it is just my opinion - I consider it a plus for users that ModernThemes uses the customizer exclusively, because that means options aren't divided between the frontend customizer and a backend options panel. Also, it enables the theme authors to more easily keep their themes up-to-date, since they are building on a core-supported feature. Sure, there are plenty of things I don't like about the customizer but all of its issues can't be fixed overnight. It takes time to improve things.