Plenty of ebooks with built-in illumination, you know.
> During the early days of CRTs, dark mode was the norm.
Yes, because they were physically unable to do anything else! A pixel could be either 100% off (black) or 100% on - and if you were unlucky the "on" was something obnoxious like bright green. The fact that basically everyone switched to light mode once it became feasible should be a hint that it wasn't just a designer fad.
> easily able to overwhelm human eyes with excessive power
The sun is orders of magnitudes brighter - even when it isn't a blue-sky day. Human eyes evolved to deal with that without any issues (that's why your pupils can vary in size), so a desktop monitor shouldn't be a problem.
The problem is contrast. If you sit in a dark room with your monitor turned to 100% brightness and you're using a light theme of course your eyes are going to hurt. It's the same with those obnoxiously bright headlights we're seeing on cars these days! Sure, you could use dark mode, but the problem can also be solved by making sure the room is properly lit, or turning down the monitor's brightness. No need to pretend dark mode is a one-size-fits-all must-have solution for "ergonomics".
The same applies the other way as well, by the way: in my experience dark mode becomes completely unreadable in a brightly-lit environment - especially on glossy screens. You're constantly dealing with annoying reflections hiding your content.
Personally I've grown fond of the way MacOS and Android handle it: automatically switch to light mode while the sun is up, use dark mode during the night. It's not perfect in every situation, but 99% of the time it gets me what I want.
