OMG... you are right, the Z system is doomed. 
Nikon employees should just quit and go on a long vacation, secretely shooting with Sony cameras and those great super compact f2.8 zoom lenses offering zero value compared to their DSLR counterparts.
When did I say anything about 'super compact' f/2.8 lenses?
Sony has compact lenses if you want them. They also have f/2.8 zooms if you want them. Not both in the same lens.
At launch, Z-mount will have neither. No fast zooms, and only three lenses to choose from, all of whose bases Sony already cover and more. They're pushing into a crowded map, not empty space.
What if...
- The Nikon sensor were close to one stop better noisewise than the Sony one?
Except that they're not. We have recent sensors to compare - D850 and A7r3 (and the A7r3 is already a last-generation design, being the same as the A7r2 sensor, but with better supporting hardware). What makes you think Nikon has suddenly come up with a next-generation super-sensor that Sony can't match, while somehow still managing to
manufacture that same sensor for Nikon?
- Adapters were released that enabled the remaining Canon users to adapt their lenses on the Z with good performance?
The same adapters already exist for Sony bodies. Most people who intend to switch and bring their lenses across have already switched. The rest are sticking with Canon SLRs and will only switch when they have to (when Canon ditches EF mount and goes mirrorless - provided they even ditch EF mount). The thing is, that doesn't mean they have to switch to Nikon - Canon, Nikon and Sony mirrorless systems would all be valid options, similarly-performing adapters would be available for all, but only Sony currently has a comprehensive list of native lenses.
- The Nikon AF mirrorless technology were able to drive natively F mount lenses without loss of performance?
You may as well ask for magic - this is an engineering impossibility.
SLR lenses have motors designed for single, large movements, not continuous, small, rapid movements. They can't take advantage of all the focus tools used by mirrorless bodies, which combine PDAF, CDAF and AI-based pattern recognition techniques at the same time. To focus the lenses as if they were on an SLR, you'd need an adapter with its own off-sensor AF system - essentially a pellicle mirror, similar to Sony's A99II. But putting this mirror in the light path costs you about a third of a stop of light and introduces reflections. So, you gain AF performance, but lose optical performance. If you don't have a separate AF system, you're then back to using the camera to drive the lens in a way it wasn't designed for, in which case you can't expect performance any better than Metabones or Sigma adapters connecting Canon/Sigma lenses to current Sony cameras.
In addition, adapters introduce tolerances which aren't there with a native lens. Due to slight movement in the system ('no movement' doesn't exist unless you weld them together), these may be slightly different each time you attach the lens. On-sensor focus systems can negate these, since they focus using the imaging sensor, but off-sensor focus systems require microadjustment, and it's hard to adjust for something when the required value is slightly different every time you attach the lens.
Finally, how much is this super-adapter going to cost? Not only do you have the body of an adapter and basic electronics - expensive enough as they are - but now you've also added a fragile and expensive pellicle mirror, more supporting electronics and an AF system that's, at minimum, the equivalent of the D850 or D500, if not the D5 (there would be little point in using it if it weren't to match the performance of those cameras). Now you've got an adapter which probably costs half as much as a high-end camera - all to attach a bunch of what would then be legacy lenses to the new system and achieve performance inferior to what you could achieve by attaching those same lenses to a D850 or D5 in the first place.
It would probably work out a lot better if Nikon gave away these adapters for free with the new cameras, as Sony did with Metabones adapters for the first few years, but, due to the complexity and cost of these adapters and Nikon's smaller size and near-complete dependence on the still camera market, it would be a much more expensive proposition for them to do so.
- Nikon did come up with native f2.8 zooms within 6 months?
If these were coming, they'd have announced them. F/2.8 lenses are the bread and butter a large chunk of working photographers - wedding shooters, event shooters, photojournalists, etc. If they were coming any time soon, Nikon would want potential buyers to know about them.
There is a long list of possible positive options that would mitigate the lack of f2.8 zooms at launch. I don't understand why you don't give these more weight in your thinking process?
Because most of them are either very unlikely or technically impossible.
