I do prefer light theme sites; the question is am I the only one who can't view a dark theme site without pain for more than a minute or two, including Netflix and similar media sites. In my strong opinion, Netflix doesn't care about accessibility, also Amazon Prime and Steam (yes even Steam hurts my eyes trying to read the game descriptions and discussion forum text).
Example
When I visit https://www.fastly.com/, try to read the high contrast dark theme, within a minute I start developing a headache and my eyes are squinting heavily.
If I do that for a minute, then switch tabs to a normal light themed site; my eyes instantly have a major weird light spectrum shift like when you're in a dark room for several minutes then someone turns on bright lights. After that, my eyes feel normal again and the headache goes away within a couple of minutes.
I asked Gemini, "which is harder to read, a dark or light theme website?", it said, "Overall, a light theme website is generally easier to read for most people, especially in well-lit environments and for long periods of reading. However, a dark theme can be easier on the eyes in low-light conditions. The choice often comes down to individual preference and the user's environment."
My office isn't particularly brightly light folks. So at least for me, that's not why dark theme sites hurt my vision.
I do have Glaucoma but I've never had any degradation (so far, thank God) resulting from it.
Looks like you're on Windows? You can run X apps with XMing, I used to do it years ago. You can run the actual X app and use it, not just get a screenshot.