Do you sit in a bright room? Right now, during the night, I see your comment like this: https://i.imgur.com/c7fmBns.png, but during the day when the room is bright, I also see everything with light themes/background colors, otherwise it is indeed hard to see properly.
When it’s dark (I can’t stand bright rooms at night), I lower the brightness of my screens instead of going for dark mode. I have astigmatism and any tiny bright spot is hard to focus on. It’s easier when the bright part is large and the dark parts are small (black on white is best).
Unfortunately, in my case, it's not a matter of lighting conditions.