No, you could do it. There is the limitation GP mentions, but that just meant you were limited in choice. Like you had to pick a text color that would look good

No, you could do it. There is the limitation GP mentions, but that just meant you were limited in choice. Like you had to pick a text color that would look good on title bars and on window background. There was however no reason software had to adhere to that. You were free to make your app as colorful as possible. Some devs were nice enough to set the text color to black but leave everything else to use the system theme, so with your dark theme you end up with a nice black on black. I think there were even some Microsoft apps that shipped with windows that had parts that were just "hard-coded" to a light theme.