Django Reinhardt didn't know shit about scales, modes and stuff, he just played what sounded good and that's the story for tons of very revered and influential musicians that the talent to overcome their lack of formal instruction (which again, most of them got later).
Your comment is just a very ignorant way to see what Pantera was about: remember that they used to play power/heavy metal before becoming the groove metal band they were known, they used to play stuff from Judas Priest for example. Dime knew how to write a song, what was he doing (just see his lessons) and how play it.
It's not different than saying Fredrik Thordendal it's a terrible guitarist just cause he seems to only know to chug the 8th string over and over. The guy was alumni of Allan Holdsworth, which is one of the most advanced guitar players ever and you can tell! his semi cacophonous and semi atonal is pure Holdsworth.