Joke aside, looks like your screen brightness is too high to begin with. If it’s set correctly, a light mode tab in an otherwise dark UI should be a mild disruption, not something that blinds you.
Legitimate suggestion: get into the habit of controlling the screen brightness and your eyes will thank you. There are DDC utils that let you control the hardware brightness (and other parameters too) of the monitor via software. I for example like ClickMonitorDDC (works well even if it’s practically abandonware), you can do things like scheduling based on time of day and controlling multiple monitors simultaneously.
I wish it were better integrated into GNOME / KDE so I could simply use the brightness controls on my keyboard.
I set my brightness to maximum because I work next to a window, but it’s the power of a million suns at night, especially on a high-end, colour-accurate monitor
In my experience it’s pretty well integrated in both GNOME nad KDE I had to work to work with a plethora of keyboards on both and they always worked if I remember right
