Well polished
The Sony has clumsy interface and ergonomics. Yes, the Nikon is better in those respects, and I have handled the Sony.
Highly subjective as Sony owners can say the same to Nikon or Canon. It will take time to get used to a new system. Not familiar with modern Nikon interface so only can compare to Canon system that I am very familiar with. Personally it's not my taste to have many physical analog buttons/switches on a camera body such as a dedicated ISO button/wheel that only slows down operation.
I am a 10-year savvy Canon owner and still own Canon 1D III that basically is the same as 1Dx line in ergonomic, button layout and shape. Personally I hate those dual-function buttons that I never can remember in muscle memory especially if in rush operation. I can make all necessary changes (I only shoot RAW) much quicker on Sony bodies such as ISO, EC (I know not that straight to make such change on Canon DSLRs). Then even AF navigation is not easy on Canon bodies - first you need press a (again) dual-function button (with picture viewing magnification) first before you can move AF point around. And you only can move horizontally, vertically or in circle but not diagonally, that something it's much easier with Sony joystick that not only you don't need to push any button first but you can move in any direction and diagonally. Then C1-C4 single function buttons are well placed (that not close each other) and very easy to remember. Also 4-direction push and central push on the back dial wheel. As a matter of fact, I can do everything including browsing menu without leaving eye in EVF that something I just cannot do with Canon DSLRs. MF is way easier with Sony bodies. And it's funny that Canon TS-E lenses are much easier to operate on E-mount than Canon own EF-mount.
When someone talking Sony menu sucks, he may not realize Sony has much more features including video than his Canon or Nikon DSLRs (exclude D850 probably). Nevertheless now 'My Menu' is great that is better than my 5D III and 1D III's one. To be honest although 1D III does balance EF 70-200L/2.8 IS II, EF 100-400L IS (I and II) and 500L/4.0 IS (that I used to own all) well, but it is also a pain to hold in many hours that my fingers got a bit of numb against a brick-like flat surface. I have no problem so far with A9 after holding several hours in an airshow. The same reason I had to return JbCamera Designs body-case (that I bought after got A9) as my ring and pinky fingers got numbed against a flat surface after while.
BTW, personally I have no issues in Sony bodies and handling. My hands are not small but with thin fingers so no any issue to fit into that narrow gap. I mounted a L-plate on A7r III and A9, not only for a bit longer grip but also for protection and tripod usage. With FE 70-200 GM or FE 100-400 GM attached, I added the vertical power grip on A9, not only for better load balance but for double batteries in action type photos. I took 17,280+ RAW photos in last airshow event and 2nd battery was still 32% left that is simply amazing, well above my last record of around 6500 photos from 1D III in an airshow. Nevertheless I have no issue if Sony changed the body shape in later models, but just waste current OEM power grip. Just hope not further increase size/weight much as I carry two cameras into any trips so size/weight is a significant factor to me.