This entirely misses one key part of how Windows has evolved: Microsoft is a collection of many competing individuals, not a single entity with unified goals.

This entirely misses one key part of how Windows has evolved: Microsoft is a collection of many competing individuals, not a single entity with unified goals. Windows development is shaped by a small team of developers and designers being influenced by a large battery of project managers and stakeholders. Their business is compromise, not uniformity or singular vision. For instance, Windows has to support both touch and keyboard/mouse because of the tablet PC group desiring equal marketing and development focus so as to not devalue the tablet brand and ecosystem. Windows doesn't have a coherent design language because it doesn't help everyone or any group particularly well. The Windows 8.1 upgrade had store login required because the app store was lacking traction. While Jay's UI ideas have great intentions, they're not solving any of the immediate problems Microsoft's groups have.