macOS Mojave announced that you’ll be able to switch all apps to dark mode (as soon as they support them, of course). But is it better? Trick is, it depends. Dark mode is definitely beneficial for media content (Photos, Illustrator, Movies) but sucks for anything else where text is involved. Nobody wants to look at white text on black background.
So, instead of switching all apps at once, it would be better if media apps would always launch in dark mode and everything else stayed the same (light).