"I have a greater appreciation of the importance of rock and roll rhythm/beat/rhythmic pulse that gives it music it dynamicism and energy after listening to Ella Fitzgerald music which was missing it."
Well, it's not rock- it's jazz. It doesn't march, it swings. And simply adding lyrics (which were generally done long after the original composition had been written, especially in Duke's case) and a vocalist doesn't somehow transform the music into "pop music" as you're calling it, it's still jazz and should be listened to as such. Ditto with the Gershwin and Berlin sets, though I'd agree that those are less successful, mostly because as you say, those 2 composers are more hit or miss than Duke is.