Oh holy.
People act like dark themes, or theming is a relatively recent invention. But in fact, Windows 95 and even earlier were already entirely themeable, system-wide (well themeable is a bit of an exaggeration, you could modify the color scheme, but still...). But the quoted problem is exactly what was already happening back then to basically prevent you from ever deviating from the default colors too much. Sure, you could make the default gray background a little darker or brighter, but I remember I tried doing white text on black background, and after a couple days I encountered enough programs that at least in some places hard-coded black text but used the system default background color. What worked a little better was programs that forced both, some text editor forcing black on white, but that looked pretty jarring too, contrast-wise. Switched back to default colors and never bothered again to this day.