We should go back to system color (usually medium grey) as the default background for webpages. Not sure why more recent browsers have replaced it w/ white, this makes for pretty poor usability/accessibility.
Similarly, I wish the app itself enabled Dark Mode on Mojave. File save/etc dialogs are awfully white in a darker environment.
(More broadly, I wish Apple would allow things like file dialogs to force to dark mode. I know you can set NSRequiresAquaSystemAppearance to NO, but it tends to mess up a bunch of other random stuff too)