do NOT spent your time on something like Darkmode, it is not neccesary !
Focus on fixing bugs in ROS and prepare for ROS7...
You may prefer the bright white interface of winbox, you may even like all-white walls in your home, you can paint your home all white if you want. No one is asking you or telling you that you have to do otherwise, and the same with winbox, I'm not asking they switch away from the theme that you prefer to work within, but asking that some accommodations be made to those who don't particularly care for it, and who don't personally enjoy the experience of blinding white lite coming off every surface they see.
Why should your personal preference be the only one that matters?
Why should it offend you if I'm given the option to choose a working environment that's pleasant for me when it would affect you in no way whatsoever?
As a user stated below, I'd even be perfectly okay with an external config file that I could write myself to override the defaults, if Mikrotik would simply just allow for it.