Same tired old (and wrong) "market share" meme
"Despite increased smartphone sales overall, Apple’s sales and its market share for iOS have fallen" - yes, due to off-the-charts iPhone 6 and 6 Plus sales (due to switch to bigger screens), Apple's year-over-year quarterly sales have been down. And that's the only reason this tired, old "iPhone is doomed because of down sales, market share" type of article is possible. In another quarter or so, when iPhone 7 will be compared to the previous year's iPhone 6s, sales will be on a positive trajectory again.
The comparison with "Mac battle with Windows" is nonsense. Mac lost that war because it and IBM PC came to the party around the same time - and the lower IBM PC prices caused more folks to buy more of those computers - which attracted more software developers. A virtuous cycle ensued - and Apple, without much software, was left out in the cold. Contrast this with the iPhone situation: Apple was to market first and attracted lots of developers because it was the only game in town. By the time Android came around, lots of software was already written for iPhone and lots of developers were making lots of money off iPhone. Even today, despite Android having 80+% market share, app developers make nearly twice as much off their iOS versions of apps than they do off Android.