I'm still using two D800 bodies and liking it. Favored lenses include the 70-200 FL; 28/1.8; 24/2.8 (! talking of old stuff); 60 2.8 AF-S macro; 300 PF, occasionally accompanied by a 1.4 converter; and 70-300 AF-P (thanks Nikon for upgrading the firmware on the D800 to work with this four years after the camera was discontinued).
What I'd like to have that the D800 doesn't have?
On-sensor PDAF......
A bigger buffer......
wider coverage of cross-type AF sensors.....
A quieter shutter......
A better designed hand grip......
A viewfinder and/or (preferably "and") Liveview/EVF that makes manual focusing "pop" a bit more.....
What most new cameras do not have that the D800 has?
Near-instant response to the shutter release. The lag time on the D800 is incredible, up there with the D5 and the best all-mechanical film cameras. I believe it has tested around 40 milliseconds. The D810 and series I z-bodies are noticeably slower. Even the D850 might be a hair behind. I've not tried a series II Z body.
What you notice missing from my wishlist?
Basically sensor performance; it's already so good that anything extra is just gravy. Or an excuse to do any kind of mass-production or non-critical job with a smaller file size in some way. The D800 is what finally weaned me off film for good.
Essentially the D800 is the digital F100 that I wanted. I am hoping, though, that the D850 has a DSLR successor in the pipeline, and that it addresses the on-sensor PDAF. I was quite surprised that on-sensor PDAF was missing from the D850 to be honest, even though the D850 checks all the other boxes on my wish list, and because of that, I decided to stick with the D800 for a while longer.