I don't think Mad Men is the greatest thing in the world, but sometimes the importance of character development can be overstated-- people get too caught up in the norms of what shows usually do and treat them too much like necessities (plot development, character development, etc.)-- Mad Men did a great job of using its characters (almost like distinct and clearly outlined puzzle pieces rather than dynamic/fluid entities) to cleverly ruminate on and explore certain subjects/moments in interesting storytelling-exercise ways that at times felt surprisingly tasteful, tactful, and artistic (not every episode, but frequently enough). Something like Breaking Bad is very straightforward and shallow in comparison even if its characters change more. The form of development the characters undergo is serviceable, but isn't that impressive, IMO-- Like, desperation and bad situations cause good people to do bad things, get lost in the thrill/empowerment of it, and lose their moral center-- As an idea, that's not really that original, interesting or worth exploring-- it's basically just the backstory of any bad guy you come across these days, and that's pretty much the focus of the entire show (which feels more like a giant excuse for edge-of-your-seat shennanigans). There are things about Mad Men's storytelling that sometimes feels too hokey and soapy (like the flashbacks and the twists), but the way that it focuses more on culture, circumstances, and worldviews has much more substance, IMO.