This is way too old school for me (and I've been developing with JS/CSS since 1997 and HTML since ... before that. On my site I just use prefers-color-scheme a

This is way too old school for me (and I've been developing with JS/CSS since 1997 and HTML since ... before that. On my site I just use prefers-color-scheme and have a toggle to switch light/dark it if the user wants, persisting the choice locally. I detect Dark Reader and honor the user's choice with that. What would you do if you had the option to choose any font of your choosing? What color for the headers? The background of the buttons? Should you be able to define the border radius? The CSS transitions? All of CSS? You can do that. There are extension for that. I don't think this is a concern for the vast majority of users.