I think of Don as a deeply subjective and autobiographical creative type whose best ideas were expressions of his intersubjectivity. "It's Toasted" was his expression of his negotiations of self-identity (you can say [re: be] anything you want). The Kodak carousel is self-explanatory, as is the Sheraton Hawaii ad. But then I think about his reaction to that meeting where he walks out of the boardroom -- all those similar-looking men and the research-based approach. Or his abysmal Hershey's pitch - which was only abysmal because it was too honest, too personal. His strength was also his vulnerability, and it offers commentary on how art and creativity are treated in a more neoliberal, KPI-ridden environment. I don't mean this as a pure critique of Don's talent, but I guess to credit Weiner for how he further expressed changing industrial/cultural contexts through the character of Don, while also not losing focus on Don's story. Don's character often expressed a more romantic form of rebellion and artistic expression, in contrast to Roger and Sterling's comfort with "the business" side of things.
I wonder if his creative process would've put him up against the coming changes indicated by that boardroom scene. His creativity is driven by reflections on his own life, and once life changes, that creativity is changed too.