It appears you need to work on developing skills because the details you espouse are not a camera or lens issues but they are operator issues. I can work with almost any camera and almost any lens because as long as I understand the controls I can make a proper exposure and composition.The only time I would use a 24-70 at a zoo would be a petting zoo. You normally need at least 200mm f/2.8 to a max of f/5.6 to get good creature images. Shooting through glass presents its own challenges. Personally. my favorite zoo lens is a 300mm f/2.8 and I usually shoot wide open - handheld as slow as 1/60ss. I do sometimes use a monopod. a 24-70 lens is a great lens and one I use often for non-zoo shooting. Your posting sounds like you are a person of experience with the expertise to critique camera equipment for the benefit of others. It is my opinion that you don't know squat about equipment, technique or composition.

Had the opportunity to test a Nikon 24-70 f/2.8 non-VR on my d850. Had it to three different venues: shot the dam site on the Wisconsin River at Sauk City; went to the zoo in Madison, WI; went to the River Walk in Naperville, IL. Each had a different challenge. First off the Nikon 24-70 felt almost foreign to me; every time I wanted to change a setting or manual focus I felt I had to hunt for the adjustment rings? Was curious why the lens moves its front element the way it does? Overall initial impression, that is NOT a walk around lens for hand held shooting under less than ideal conditions; not without VR anyway. And it's NOT a zoo lens either. I got some nice shots at the dam site, then it was a decent afternoon with broken clouds to break up the monotony of the late September sky. Shooting conditions at the River Walk were not the best because of mostly overcast skies so I was limited to what I could do without a tripod and get sharp shots; I had intermittent rain. Auto focus worked best at the dam, probably because the lighting was better. At the zoo I had to do a lot of shooting through glass without a tripod. I had a comparable Tamron a while back that I returned to B & H because my old manual focus primes gave me as good if not better/sharper images with a whole lot less weight to deal with. I was expecting a whole lot more than what I have seen so far. MY OPINION!