Ken Rockwell: Don't buy a midrange zoom. Carry a fixed 50mm instead, like a pro.

Seriously you are not doing justice to KR. He did say what you said, but he also added that you should complement with a ultra-wide to wide angle zoom + telephoto zoom.

KR is not stupid. a 24-70mm at 24mm is very different compare to a 50mm. No way how you back up or twist. you will never get what 24mm can do? 24mm vs 50mm is just different, the angle of view is just very different. But 50mm compare to 70mm is very close. Although at 70mm it compressed more image, I'm not good enough to tell difference. But 24 vs 50, it's very different. Everybody can see it.

to sum it up. he said buy a ultra wide to wide zoom + 50mm + telephoto zoom.

instead of ultra wide to wide zoom + medium range zoom + telephoto zoom