True, but at a given resolution, with CSS turned on, and in dark mode all users will basically see the same HTML view. The user can't have a dark mode HTML page unless the web site offers one or the user has an extension that makes a best effort to create one. HTML with complex Javascript rendering makes it hard to give the user control.

The concept of a user agent that gives the user much greater ability to choose how they want to view content could mean each user will:

* Pick their own font, font size, line spacing, margins

* Pick their own text color and background color. Like dark mode, high contrast, etc.

* Choose how linked images are shown: inline, click to load, load in new window, expandable thumbnails, etc

* How sections, section headers are displayed. Add a table of contents? Add a button to jump to the next section? The user can choose.

I like reader view, which gives me the ability to choose how I view HTML, but only when reader view can figure out how to extract the content (sometimes disastrously missing paragraphs of text...)