I don't think being self-taught makes you less capable of writing complex music...
I don't think he wanted to say that..he meant the same thing you did.
They are techincally very strong, but not the strongest (as the already cited Cynic could be) but, most important thing, they know a lot about theory and this is a great advantage; someone could be the fastest guitar player on the earth but without knowledge 'bout what you want exactly to do it's quite unuseful..