I have used the black/ screen white text on my Kindle app in my iPad for years - especially reading in bed with the lights turned off. A bright white screen in the dark really is an anathema.
This is why I only use dark themes in a dark environment. Of course I don't use my phone a lot once the lights go out when I'm ready for bed, but when I'm in a cinema and I text before the movie starts, having a dark theme in Telegram is useful. Similar to how Google Maps in a dark theme is great for driving at night. I just don't like using dark themes during the day.