The Settings app in Windows works very well with mouse and the wasted whitespace only appears when it's maximized, the app was made to be responsive with several windows sizes.
Seems like you've never used it with a non-FHD screen. Or as a window. Because it absolutely wastes a ton of space. The sidebar on the right will disappear to the bottom, which is unnecessarily cut off because of the crazy large margins around everything. I don't understand why every page needs to be scrolled when the Control panel fit twice as much functionality into half or even a quarter of the space.