Not sure what's there so hard to understand.
Whats hard to understand is that nobody ever uses all the features of their tool, at least not with complex tools that are prepared for many different useages. Which was already true for the D800 and D810, which have already been very useable for many fields, and actually probably even more so with the D700.
Meanwhile the D850 has a lot more to offer than just 45 Megapixels, which, granted, I wouldnt need, for example:
- Very good build quality
- Very good viewfinder - more magnification than any of the D3/D4/D5 models
- Excellent image quality, even better than D810
- Very good high ISO - quite a bit better than my D750
- Base ISO 64
The good build quality alone attracts me a lot. After the D600 and D750 I really could do with a camera that just works for say the next 5 years.