As a software developer, who codes about 15 hours a day (day job and personal projects), I ditched "light mode" many years ago as it's too harsh on my eyes to be staring at a bright white screen that many hours a day. Dark mode is far easier to look at for long periods of time.

I have no trouble reading code in dark mode in a well lit room. If it were difficult to read, it wouldn't last 15 minutes for my needs. I don't code in "D4rK M0D3" in the dark, I'm not a l337 H4CK3r.

>Ever try to read a dark mode UI on your phone on a bright summer's day?

Phone in direct sunlight is one thing. That isn't the way most people use devices, that's a more rare use case than sitting at a desk 8 hours a day staring at a bright screen. There are also high-contrast modes for eyesight challenged people, which can be used effectively in bright sunlight too, but I'm not going to code that way for hours a day if I don't really need to. Phones and other devices also have adaptive brightness, so if you are in a dark room the phone's display brightness is going to be dimmer automatically, and I'm not really sure you know the difference between "dark mode" and "brightness turned down". So using a phone screen and high contrast required for using screens in direct bright sunlight is a poor example to support your argument. Maybe you also need to qualify all of your arguments with "on a mobile device in bright sunlight", because that isn't the main use case for "dark mode".