Dark and light mode are not symmetrical

The terms dark mode and light mode sound symmetrical. If dark mode means that every background is dark, light mode must mean that that every background is light. At least that's how it's implemented in Windows, ChromeOS and KDE, where even the taskbar has a light background in light mode.

Instead of thinking of dark mode and light mode, we should think of dark mode on or off.

If dark mode is on, every background is dark. If dark mode is off, backgrounds can be light or dark.

Colors mean things, and unless we're in dark mode we shouldn't restrict our palettes of colors and meanings.

Light means professionalism. Dark means fun. That's why an office app uses light backgounds while a game uses dark backgrounds.

Dark means privacy and anonymity. That's why an incognito window uses dark backgrounds.

Dark means hacking. That's why a terminal uses a dark background.

Light emphasizes. That's why the taskbar should have a dark background to deemphasize it, to allow to focus on the app you're currently using, rather then the operating system, and whatever other apps you have open or pinned to your taskbar.