If they were being held back by the "legacy" parts of the OS, you might be right. But they're not being held back, rather, it's their unique selling point..

Arguably the legacy bits are the bits that work, the modern bits (UWP) are barely seeing any adoption. They're force feeding the modern bits, presumably because they've lost the human resources/mindset/talent to maintain the legacy bits?

This strategy of arm twisting coercion has failed them before and it will fail them again, and again, and again.