Maybe you’ve been using themes with too much contrast ? I mean, I can’t work on a light theme for any extended period of time, but most dark themes are too stark and eye searing for me, so that may be your case too?
Mine sure aren’t with light mode, even in brightly lit office environment. Different people have different eyes, and needs. What may be an unnecessary gimmick for you may very well be vital to the next person’s livelihood.
Wait did you really take the retina thing literally ???