I want contrast

Sure, but you can also have contrast with a dark background that isn't constantly shooting a third of the photons your screen can generate (or more, since in some screens blue pixels are the largest), and the most energetic at that, at your eyes... high contrast themes tend to have a black background (not a gray one like most dark themes) precisely as a way to maximise contrast...

(It was even worse when we sat all day in front of a fucking particle accelerator, of course; frankly, as much as I loved CRTs' ability to work with multiple resolutions I don't know how we didn't all end up going blind...)