Apparently, something internal to how the OS handles mouse scrolling was changed, and only the Magic Mouse gets a proper scrolling experience using built-in drivers. It is possible to fix this, but only with custom software (either drivers for specific mice or general tools for all mice).
for it to be any smoother, there would need to be some artificial smoothing of the scroll wheel input. and i'd rather not have that.
For example, when using the wired Mighty Mouse, the same motion of my finger will sometimes scroll a couple lines and sometimes scroll the entire page or not scroll at all. The same mouse plugged into Windows does not exhibit this problem.
This is not normal and you're possibly facing a bug. I have a Master 3S and mine scrolls exactly the same distance with every click of the wheel.
I don't have any Logitech mice anymore, but maybe they've learned how to speak to Macs or worked with Apple to make them better. I had Logitech mice in the past, ca. 2-3 years ago, and they had the same problems then. I did notice that plugging in a non-Apple mouse results in a "Setup Your Keyboard" prompt, which I just quit out of (it's not a keyboard...), but maybe that would install a driver if I followed through? Though, the Mighty Mouse is an Apple mouse, and it still sucks on macOS but not on Windows.
And yes, fixing this requires custom software.
This is not true. Again, I have a Master 3S and I have natively, through macOS settings, bound Mouse 4 and 5 to mission control.
It is not my understanding that Apple has any responsibility for ensuring equal access and capabilities for third-party accessories on their own weird, proprietary, invented-in-house computing systems.
Therefore, it is also not my understanding that they can be negligent on these matters.