My problem with RT is that the ordering of its operations (an absolutely crucial thing) is not specified anywhere. It's just an explosion of sliders, more or less arbitrarily grouped into categories. Same goes for ART, the somewhat streamlined fork of RT. In contrast, DT offers a sane and documented pipeline, which reasonably follows the pipeline known from the video world, with its separation into scene-relative and output-relative parts based on physics and perception, adjusted for photography needs.
Strict terminology based on fundamental principles, strict reasoning and control over the pipeline, rooted in the video world. Perhaps that's why it looks somewhat foreign to you, it's a bit unlike most other photography tools which need to be marketed and typically offer "magic" with little reproducibility from one software to another. Like the saturation slider which is not actual saturation known from the color theory, at least in Lightroom and C1. Hence the endless bickering between photographers who don't understand fundamentals of color perception and fight over what software gives a better look.
Regarding the UI, maybe I'm different from the most but I honestly don't care how it looks, as long as it delivers and is usable. A professional tool is a truck, not a luxury car; it's alright to have it a bit dirty. I remember the days of Softimage 3D; when I've seen it the first time in 2000, it looked terribly ancient to me. But it was one of the most powerful CGI toolkits at the time.
Regarding the defaults, they are easily changed once and are used afterwards, provided you understand the fundamentals. However I've never needed to do so once I understood how it functions under the hood. The defaults look fine to me.
I'm not a professional photographer though, and despite DT being light years ahead of everyone in several areas I find it lacking in others, which prevents me from using it on a constant basis.