That is a tricky word.
In a couple of years the trends will change, and you’re going to start complain about the outdated dark theme.
Don’t get me wrong I prefer dark themes, I use dark themes everywhere, but there’s nothing wrong with the controls. They just have to re-create each icon to make the background and foreground (picture) changed by the user. They already have the option to change the colors in Rhino. Icons is the only issue, because the foreground on most of them is black and if you make the background black you can’t see what’s there.