I also was a big fan of Windows Phone. It was a good OS and the live-tile interface was brilliant. Also agree the introduction of the hamburger menu was confusing and pointless in replacing something that worked.

I don't think MS had any confidence in anything they were doing over that time because they never seemed to properly commit to anything. Win Phone could have been bigger and competitive if they'd focused effort on it (marketing - and no not MS's standard marketing 'quality,' app dev funding, etc)