Yes. Chang had wild talent as an overall athlete (eg. quickness, balance, reflex etc) and, more "talent" mentally than Lendl, and even Connors. He is one of the very few (possibly only) who can claim his determination, and drive was greater than Connors.
Having said that, it is for exactly those reasons, that we know he maximized his potential....and it wasn't good enough to be a multiple grand slam champion like Lendl and Connors. It was good enough to be one of the very best players in the world, for many years, at a height of 5'8, during a very competitive era, so he should be proud of that though.
I am always reminded of someone asking Mcenroe what a "couple of more inches" would have meant to Chang's career, and Mcenroe saying "if he were a couple of inches taller, he would have been Jimmy Connors."