As an anecdote, I have a Sony a7r and operating it via its mobile app is one of the worst user experiences I have had in a while.
Same goes to the surrounding ecosystem of software. E.g. Adobe's Lightroom is full of obsolete paradigms and weird usability choises.
What always stood out most for me compared to Canon was Nikon's larger viewfinders, letting you commit to actual photography rather than being stuck with a feeling of peeping through a keyhole, and placement of buttons on the camera body allowing for maintained control of the most necessary functions (shutter speed, aperture and even ISO) without having to change your grip or move the camera away from your face.
Canon bodies are designed by engineers, who all had to prove they could palm a cinder block in order to get hired.
Sony bodies are designed by the cinder block.
On the digital front I found Fuji X-Txx series to be like tiny Nikons in their usability with all common controls on dials.
(One reason I shoot Nikon is because I can still shoot his glass on modern bodies. Indeed, that's what my D5300 spends a lot of its time wearing these days.)
True revolutions in consumer imaging excepted, I doubt I'll feel more than an occasional gadget fan's urge to replace my D850 and D500 as my primary bodies. Oh, the Z series has features, I won't disagree, even if I'm deeply suspicious of EVFs and battery life. But the D850 is a slightly stately, super-versatile full-frame body, and the D500 is a light, 20fps APS-C, that share identical UIs, lens and peripheral lineups, and (given a fast card to write to) deep enough buffers to mostly not need thinking about.
For someone like me who cares very little about technical specs, and a great deal for the ability to hang a camera over their shoulder and walk out the door and never once lose a shot due to equipment failure, there really isn't much that could matter more. I may have 350 milliseconds to get a flight shot of a spooked heron, or be holding my breath and focusing near 1:1 macro with three flash heads twelve inches away from a busily foraging and politely opinionated hornet. In those moments, eye and hand and machine and mind and body all must work as one to get the shot, and having to think at all about how to use the camera essentially guarantees a miss.
Hence the five years of work I've put into not having to think about that. I suppose I could've done more than well enough with any system, sure. But my experiences with others have left me usually quite glad Nikon's is the system I invested in.
After all, most of the time she's watching me every bit as closely as I her, and I like to be able to show that. From the ways people look at and talk about that work, the effort has not been wholly wasted, but it is a more demanding task than I expect a median EVF, or if I'm honest really any even remotely affordable model, to handle. My eyes barely handle it, such that even in the D850's bright and generous viewfinder, the way I perceive this kind of focus is not as a clear sense of seeing those fine divisions between optical elements, but rather as minimizing a sort of unpleasant perceptual "static" or "interference," and it doesn't work at all even in my dominant eye through the lens of my glasses. (My cameras' eyepieces have diopter inserts adjusted to match my prescription.)
On reflection, maybe that's why the EVFs I've tried (Nikon Z5 and Z7 iirc, so previous generation) felt like they had a kind of weird shimmer I didn't like. I assume the Z8 does better, and sure, all the focus peaking and trick shot stuff in the viewfinder is nice. I'll even grant it feels like looking at the future. It's just that, so far at least, I find I seem to prefer looking through a camera.