Not just the app, but also the browser.
Also, in my experience the Windows Phone hardware was dodgy. The first one I bought was a Dell and failed under warranty…and the replacement failed out of warranty. Then after an LG Android, I bought one of the last Lumia’s. The camera failed just out of warranty. Then the whole thing failed while I was traveling.
So I bought an iPhone.
I end up on Android simply because of file drag and drop and an open App ecosystem which they are now trying to lock down.
I never could understand why MS would not put heavy muscle behind it. Maybe they deep down knew hardware execution was not their strong suit. People think the software was the problem, but I think if MS really believed in the product, the software side was eminently solvable.
It felt like once they dropped mobile, their whole direction become misguided. Also UWP made sense when there was also a mobile/tablet side to it, could even deploy those apps to the Xbox and it kind of worked. But then they kicked out that supporting support and suddenly they got working on trashing what good Windows still had.