xeleh
What if, "high contrast" instead of "dark"?
The linked issue tracker says that it should not have "a perfect recreation of the Dark Theme". Well, maybe their nominal objection (although, we suspect their actual motive is something else...) is that the theme is their intellectual property (copyright). But what if you add a high-contrast theme instead? A lot of IDE's now provide that. For example, IntelliJ-based IDE's (such as Android Studio) have that, and Visual Studio Code has that. I have been using such high-contrast themes, because usually a "dark theme" makes texts difficult to read (grey text on darker grey background) when the screen brightness is low.
So, if you add a high-contrast theme, for what reason can they ban it? Unless they have an explicit rule that prevents modifying the looks of the editor's UI... You could even argue that this is actually an accessibility feature. Some people do have a vision problem that cannot discern low-contrast objects...
https://user-images.githubusercontent.com/42638450/56735796-1b20f700-6784-11e9-86b5-d6264ca9add5.png
Take a look at https://github.com/kamyker/UnityDarkenThemer. That project seems to be already focused on the kind of customization you describe.
