and guess what, it's far easier and more pleasant to use all contrast available in color and tone it down with the brightness setting of the monitor, than doing grays on grays and having to shade or crank up contrast in the monitor
Yes it does depend on lighting, see my other comment.
No, ‘Maximum contrast everywhere’ given as a directive without consideration is not a solution and will increase the problem.
Consider things beyond HDR displays: At technology progresses, we will approach superbright display technologies which will surpass the dynamic range of the human visual system. Technically, these will be as bright as light bulbs and brighter and could be used as such. Going by that max brightness directive, we will all stare happily into a direct light source one day. Or one is happily busy dragging the brightness slider up and down the whole day, one at a time for every app and site. It won’t work. To solve this, we would need tone mapping at the latest pipeline stage, everywhere. And this will, of course, again reduce contrast, but this time, by design.
The other major problem is: by leaving it all to the users (all three dimensions of the now prevalent color model), one throws every standard out of the window. One website will send out 4000 nits, the next one 350. One display can handle it, the other cannot. Color shifts abundant. How should that be accounted for?
Furthermore, your model makes it impossible to design for: this removes the visual target platform and puts legibility and qualitative design principles at the mercy of technological progress. So solve this with the tech available, there were several agreements made to specify calibration targets - which include brightness and contrast settings, aka gamma in more than one dimension.
In a perfect world, no screen would leave the factory without a built-in calibration device and an ambient light sensor.
One more problem, the constant intermixing of use cases while discussing HDR displays: not every use case needs an HDR treatment. It does not make any sense.
The main problem HDR solves is that content creators are not forced to squeeze 10 pounds into an 6 pound bag anymore. And if your display supports this, you can benefit from the full color space the content creator wanted the observer to see. Which is totally nice for hundreds of use cases. However, staring at a pitch black font next to a white background which emits 20.000 cd/m^2 would be painful.
This both ignores that color calibration is a thing, and that the hypothetical 4000nit display will still have a brightness setting, and ignores the pain of real users with real 250nit displays
and guess what, it's far easier and more pleasant to use all contrast available in color and tone it down with the brightness setting of the monitor, than doing grays on grays and having to shade or crank up contrast in the monitor