From a UI/UX point of view, I am on the opposite side of those who are against pure black or pure white. However, I don't think you should have pure black against pure white background, primarily because the contrast ratio of 21:1 is quite sharp. I think a contrast ratio around 18:1 to 19:1 is a little more soothing to the eye.
The question is which one would you go off a little bit? In this site itself, the text is not pure black but
rgb(36, 39, 41) but the background is pure white.
I think it may be better to have it go the other way around namely have the text as
#000000 and make the background a bit warmer ; this reduces the overall blue light levels; I basically asked a question regarding Is a pure white background generally better (if the user preference is "light mode" that is)? Over say something with a lower color temperature.
However, on a black and white site you can't make it go "warmer" because to make it warm you basically reduce your blue levels as such it will break your requirement.
To put into context, here's the swatch I had generated to see the resulting contrast ratio vs the color against black text. The top row is my base color which I am using the
#f6f3e7 value at 18.893 contrast ratio. It is actually higher compared to the gray scale one at
#f1f1f1 with 18.592 ratio.