1. The market ranking has exactly jack shit to do with how useful a product is.
2. The app ecosystem for Windows is sufficient for every day work. It has mail, calendar, browser, Cortana (if you care), texting, Skype, and phone.
3. See #2
4. See #2
And for your final comment, I call more bullshit. I have scrapped more Android hardware than I have Windows phone hardware. Many of my android devices stopped getting the latest updates due to either hardware limitations or vendors not shipping updates. My windows 8.1 phone I ditched a year ago after 2 years of use. My windows 10 phone I have had for over 1 year and still receive updates.
The Windows device is uncluttered, organized (by sane categories) and predictable. My experience with Android is that it is cluttered, unpredictable, unorganized and has an app ecosystem I have to filter through endlessly to find one decent app. My experience with Apple is far less, but my limited interaction has left me unimpressed.
Not written from my Windows 10 1709 phone, but from my Linux desktop running Google Chrome. So, go ahead and call me a MS fanboy.