This is what I should have added. I'm a very long way from really knowing about this sort of stuff, but as I understand it, a larger flange diameter allows for a larger image circle diameter, which means the captured image is from the central portion of the ICD rather than the extreme edges, so can be sharper and less distorted etc. The Flange distance relates also to image quality, but something to do with different wavelengths (think colours) of light converging at different distances or something. yes, that is a dreadful attempt at an explanation I agree, but if someone cleverer can explain it, then please go ahead!
The flange distance isn't actually a huge deal other than lens compatibility at least once you get into the realm of mirrorless lenses.
Basically on a DSLR, you need space for mirror between the focal plane(film/sensor) and the back of the lens.
Why you care about that comes down to focal length of the lens attached. Basically, focal length(generally) is defined as the distance from the optical center of the lens to the focal plane when focused at infinity. On a simple lens design, the geometric center(halfway point between the front and rearmost element) is also more-or-less the optical center.
Most 24x36mm format SLRs have a flange focal distance of 40-50mm. That's not an issue when dealing with longer focal length lenses-say an 85mm or 105mm lens-as the optical center is naturally going to sit plenty far away from the focal plane and there's room for the lens mount, linkages, etc. Incidentally, you'll often find that lenses in this range of focal length are optically excellent and that comes down to the fact that they are fundamentally simple optically.
Of course this means that long focal length lenses can become unwieldy, so that's where the "telephoto" group comes in. Incidentally, "telephoto" refers to a specific optical design characteristic and is not a synonym for "long focal length" lens. A telephoto group added to a lens design shifts the optical center rear of the geometric center. Telephoto groups can be bought and used as their own separate add-on to a lens-we call those "teleconverters", but more often they're integrated into lens design. A lens designer doesn't want to go too extreme with shifting the optical center back as that introduces its own problems that can often be fixed with even more expensive optical solutions, but it's still there. For this reason, flange focal distance also doesn't really matter on telephoto lenses.
As a bit of a sidenote too since I also use Hasselblad V mount cameras-the flange distance on those is 60-some-odd millimeters(I've been working on this post way too long, this is a late addendum, and I don't feel like looking it up). The ubquitous "standard" V-mount lens is the 80mm f/2.8 Zeiss Planar. This is a big 6 element lens. It's also a slight retrofocus design. It's been widely known as long as I've been in medium format that the 80mm f/2.8 Planar fitted to a Rolleiflex of the same age as a given V-mount Planar is a better lens(plus is a simpler 5 element design and smaller). This bothered some Zeiss/Hasselblad engineers enough that they released the 100mm f/3.5 Planar-a non-retrofocus lens that's supposedly optically "perfect"(it's too rich for my blood and the 80mmm is good enough plus honestly better for my needs than a slower, longer lens).
Obviously too the mirror causes issues when you get to short focal lengths. On the Nikon F mount, this tends to start happening around the 60mm focal length, and of course as you get to shorter focal lengths this gets more pronounced. The solution to that is what's called a retrofocus design, which is essentially a "reverse telephoto" group that shifts the optical center forward of the geometric center. Even Nikon's 50mm lenses need some amount of retrofocus to work properly(and the very early F mount normal lens was actually 58mm to lessen the burden of this). Leicas and other rangefinders have always excelled at shorter focal lengths because, among other things, they can just keep scooting the rear element back further without worrying about a mirror in the way. Some early SLR lenses did this as well-they required mirror lock-up on the camera and an external viewfinder.
Mirrorless digital offers much of the same advantages as a viewfinder, but with an important caveat that's specific to digital cameras and not really a concern in film. The microlens array over digital sensors is sensitive to angle of incidence of light on the sensor. In any DSLR, even with designs like Canon EF-S lenses where the rear element location takes advatage of the smaller mirror possible in an APS-C format camera, there's no concern of the rear element being close enough for this to happen.
In any mirrorless digital, whether rangefinders or EVF cameras, that concern/possibility is very much there. Still, though, in general normal to wide normal lenses(say 35mm-50mm), which would be retrofocus designs on a (D)SLR, can be simple lenses. Even ultra-wides need a less extreme retrofocus design than for a mirror camera. Nikon has made two 14mm rectilinear f/2.8 lenses with 24x36mm coverage I'm aware of-a prime and a zoom. Both are big lenses, the zoom especially so, and are not particularly strong performers. There was also the 13mm manual focus prime, which is optically superb and almost totally distortion free(something the designers care less about in digital era lenses since it's so easy to fix in post or even in-camera) but is massive and also relatively slow. Everything I've seen of the Z mount 14-24mm f/2.8 is that it's smaller, lighter, and better than the F mount version.
And this to me is, optically, where I seem to see the most improvements in mirrorless optics. The teles I've seen look to be at best incremental improvements over their DSLR counterparts, and honestly if they were made in F mount I expect once wouldn't see much difference in their performance between say a Z7 and a D850. It's also telling to me that one of the more recent marquis lenses-the 120-300mm f/2.8-was made in F mount, although most speculation was that this was a 2020 Olympics prestige lens and for most Nikon invested sports photographers the D6 was going to serve them better than any Z mount camera then available. The D6 comes up short in resolution and absolute frame rate compared to the Z9, but everything I've seen is that it's a very capable camera for action and especially with focus tracking.
One other thing-the f/.95 Noct-Nikkor I'm pretty sure would not be possible on the F-mount thanks to mount diameter. If it were I expect Nikon would have made one as Canon made an f/1.0 lens in EF mount(the Canon and Leica f/.95 lenses were rangefinder lenses and free of retrofocus limitations).