I don't think the problem was primarily the lack of apps but a major reason to use Windows mobile. With iOS you get the high end hardware and deep integration with Apple's ecosystem. With Android you get deep integration with Google's services and a wide range of devices in prices and features. What did you get with Windows mobile?
But MS services weren’t as good years ago, and they didn’t have many apps, and they kept burning people by not letting them upgrade to a new major OS release.