@MattSuda, I have done Dark Mode this way so that I can get it shipped.
Building a Dark Mode that is light-text-on-dark-background requires a complete UI redesign, with every element in the app being changed, and the related UI code modified or rewritten. It’s a lot more work, and takes a lot longer.
Doing it this way meant that I mostly only had to switch out the background colour and switch the map style. It meant I could get Dark Mode support built and shipped in less than a month.
Is it ideal? For many people, probably not. But it does make the UI less intensely bright in dark environments, and allow for setting different custom map styles for Light and Dark Mode. So it is at the very least a step forward.
It also allows me to do it as an iterative process, with this step laying the foundations for a potential later light-text-on-dark-background version. There’s now functionality for handling different map styles in light and dark mode, for example.
I could have held back this step and not shipped it, to continue leaving people with no Dark Mode support at all, until I eventually got time to finish a full light-on-dark version. But ultimately I decided it was better to ship something now than to continue delaying Dark Mode support indefinitely.