I'm 51. The "smartass/jackass/asshole" has been around for most of my life and the "old fashioned hero type as portrayed by Jack Lord" was on its way out before he filmed a single frame of his "Hawaii 5-0" pilot. A little film he was in called
Doctor No probably contributed to its demise.
Guess we didn't watch the same shows growing up, because I don't remember that at all. McGarrett, McCloud, Canon, Mannix, Columbo, McMillan, Dillon, Barnaby Jones, Ironside, and the list goes on and on, and NONE of them were a smartass/jackass/asshole. None, nada. NONE Of them were anything like this current version of H5-0.
The change you're talking about came later. Even the less "straight laced" characters were mild compared to the smart asses that populate our screens today. I didn't really watch Starsky and Hutch so I can't really remember their characterizations clearly, but I think it's probably fair to say they might have been more like that. Baretta was a different kind of character too, but it's been so long since I've seen that, that I'd be hard pressed to call him a smartass/jackass/asshole. His character was definitely more comical than a Steve McGarret for example. He may have been among the leading edge of the change.