I have been a fan of dark mode for a long time. People including myself are so invested into dark mode that everything whether it supports or not is on the dark scheme, or even worse "pure black". Every website turns black no matter what the creator had intended. Every app goes dark forcefully with mismatched buttons and forms but we still use it.
I have read many articles about people changing their display modes to 'light' and saying that "dark-mode" isn't as beneficial as we considered it to be. We all assumed that dark mode reduced the strain in our eyes and also saved battery. I cannot be a 100 percent sure and say that it doesn't.
I recommend reading the article published by The Nielson Norman Group¹ about dark vs light mode, where they have concluded that using Light mode resulted in better performance than using the dark mode for most people.
We humans evolved collecting food/hunting in the daytime and taking rest at night, our eyes are developed to be used in the presence of more light. Eyes in general are supposed to be more functional and useful when more light is present. The pupils in our eyes becomes wide when we are in an environment where there is less light, and they become narrow where there is more, but the performance of our reading doesn't just depend upon the amount of light passing through our pupil, but also the size of the pupil through which the light passes.
Our eyes just like the cameras work in the same principle (Actually cameras work in the same principle as our eyes do). If the aperture of the eyes is larger, the depth of field is shallower as a result it is harder to focus on things, but when our eyes have enough light the pupils shrink making the aperture smaller and eventually increasing the depth of field and making it easier for us to focus.
It is not that 'dark-mode' has no advantages. It has! The claim that it saves battery is correct, but only if the technology used in the display is OLED. But most laptops and display people use are IPS/LCD panels, which cannot turn off the pixels to display true black like OLED does. There is always a backlit besides the screen which glows when the screen is on even when the colour displayed is black. Dark mode may even be better for people with cloudy ocular media (like cataract) because the display emits less light as the people suffering from this problem prefer less light as more light reaches the eye with a cloudy lens, there’s a bigger chance of a distortion.
Light mode isn't perfectly good either, because there may be long-term effects associated with light mode, like the chances of myopia.
In their study, Andrea Aleman and her colleagues at University of Tübingen in Germany asked 7 human participants to read text presented in dark mode and light mode for an hour each. To see if their predisposition to myopia changed after reading, they measured the thickness of the choroid, a vascular membrane behind the retina. The thinning of the choroid is associated with myopia.
Light mode helps us focus better and also reduces strain in our eyes as compared to dark mode, automatically improving our performance and hence our productivity. But in the long term, there might me chances of myopia. Another thing is that dark mode is still required for the people who still enjoy dark mode and also for the people who are suffering from cloudy ocular media or similar problems. As of me, I will be continuing the experiment and keep changing things and try different shades of colours keeping the light theme in mind. I am a person who loves the terminal, so the terminal in light mode is going to be very difficult to adapt, but let's see where this experiment takes me.