For me, most dark mode styles are awful (jet black background bright white text). I'd rather have per website toggle so I can apply my own styling when the site's styles suck.
But you can have both? Automatically switching between light and dark mode based on system preferences is handled by CSS, which you can override with your own styling.
But you can have both? Automatically switching between light and dark mode based on system preferences is handled by CSS, which you can override with your own styling.