Well, I'll meet the dark-mode people halfway, and say that it should always be available to users who want it.
No one is saying that a personal preference for dark mode is invalid, just that it shouldn't be the default option, or worse, the only option.
There are easily 10x if not 100x as many sites that only support their default of light mode as those that even offer built-in support for dark mode, and it's more like 1000x as many as those that default to dark mode.
TFA does seem to be explicitly demanding erasure of the preferences of an insignificantly tiny minority of websites.