I miss the times, across all platforms, when you could just pick an accent color or two for things like window borders, filled radio buttons and so on. On GTK you could take someone's window theme, someone else's widget theme, and go "that, but in orange".

You could even, if it didn't come by default already, have the active title bar in a different color.

Maybe 99% of people didn't use this. Maybe they hired an authoritarian at GNOME to make the adwaita "one theme to rule them all". But it used to feel like I the style choices for my own computer's gui belonged more to me as a user.

Often, that meant picking a theme that I liked, from the very active theme-design community (the garden lists more than 3000 themes, although I'm not a mac person) and then just tweaking a color here or there.