FFFFFF and 000000 are simply too much contrast for my eyes to read comfortably regardless of which is background and which is text. I prefer a background of ECECEC with text being 333333 if I’m in light mode, or the other way around in dark mode. It noticeably causes less discomfort for my eyes.

You can adjust brightness and contrast so that 000000 looks like 333333 and FFFFFF looks like ECECEC. If that’s what feels comfortable to you, arguably that’s how it should be set.