Earlier quoted context omitted.
New software. The version of FXOS that came with the Flame (1.0) was... not good at all. 1.1 and 1.2 added some niceties that started to make it usable as a daily driver phone; 1.3 added async pan and made things feel slick; and 2.0+ were just lovely.
So.. the best of the best kind of browser people at Mozilla optimized the HTML/JS/CSS and reached their target after a while. This makes sense with my experience from Opera Software (who also tried to build a browser OS, but way back in 2003-2004 and quickly retreated after it failed): The main issue here is that writing a performant HTML-based UI is a very complex thing. It works great when people who really underst…
Of course not anybody can make a well-performing web app, just like not just anybody can make a well performing Android app. In some ways, yes, it is a little more difficult.
But speaking as a C programmer who was pleasantly surprised by the change, it's not that difficult to make a performant web app. I've never had a problem with it.