Last year's Windows 10 release was unlike any Windows release I've ever used before, and I've used most of them.
Almost every Windows release to-date had a sort of unfinished vibe that reflects the product's history. Parts of the operating system developed long ago have almost fossilized, being preserved verbatim in each subsequent release. It gives the entire operating system an overall incomplete feel.
Take Control Panel as an example. The oldest parts of Control Panel use dialogs for each group of settings, as this mouse window exemplifies. Those tabs are extensible by third parties. That SetPoint Settings tab, for example, launches Logitech's mouse app for configuring the various buttons on my Performance MX mouse. New systems to this very day continue to use this extensibility; most Windows laptops will have a tab to configure their touchpad.