[ubercow13]

Yeah that seems bad. If you choose low contrast fonts, reduce the contrast of photographs to the background by making them darker, etc, it's just like turning down the brightness and contrast of your whole site. If the user thinks the content of your site is still too bright with dark mode on, maybe they should turn down the brightness of their device?

By making everything on your site dark and low-contrast, the implication is that the user wants to see other things on the screen in higher contrast alongside your site, like the UI chrome. That seems unlikely - your site is the most important content that they have on the screen at that time and it should probably have the highest brightness or contrast of anything on the screen, not the lowest.