Yes and no - there are classes when in the hands of a well played person have a much higher success rate.
I do agree though, that in general, on equal skill footing, any class can beat any class. The problem arises when people seem "OP" when a good player gets ahold of a character that can benefit from being played by someone who serious talent.
Tank-sins come to mind. The problem is, you can't nerf them because of the skilled players otherwise the class is useless to 95% of the population.