There is more to web development than building components. There are also things like accessing a backend, building authentication services, etc. that developers need to worry about.
Are you under the impression these things aren't possible (or even easier?) with web components or vanilla JS? You don't need a big framework for any of that.
I'm building an app with Ember, and I like how it abstracts away the more tedious aspects of web development without preventing me from moving to a lower level of abstraction when I need to.
I've built a small app in vanilla JS, so I know what the alternative to using a framework is like.
Doing XHR by hand is not easier than using Ember-Data.
Writing custom JS components is not easier than extending Ember's Component class.
First of all, let me share a wonderful (and performant) mobile app, written in ember. It uses ember-data to connect/normalize the iTunes api, and provide a slick fast mobile experience.
Disclaimer, I work on & with Ember.js (and I didn't work on https://fnd.io)
I've worked on several mobile web apps using ember, and performance did require being careful, but often "being careful" was nicely aligned with the mobile UX people expect. Small screen, put less stuff on it. etc.
Often times, we do see issues with ember on mobile, typically this is due to deeply nested loops of UI components being rendered. And most often, performance on mobile was an after-thought.
PSA: Regardless which framework (or no framework) you use, if you are shipping to mobile. Test/develop on your target mobile devices from day 1, you will not have any surprises, and you can catch performance related issues before they fester.
As for the discourse post, there are some issues ember is working to improve. If one reads further, it outlines the largest concern being the growing gap between JSC (Safari, which offers near desktop performance for discourse on mobile) and V8 (which doesn't do so well on mobile for discourse) performance. Year over year, the iOS experience is improving, but the android/v8 experience does not appear to.
The TL;DR of the issue (as is currently understood), is JSC handles dynamic code better, whereas v8 does not (yet) and Ember should both reduce the dynamism and continue to do less work. Which will continue to improve the experience for all consumers.
This is actually quite an interesting issue with lots of details, I could go on, but this is likely not best place for anything in depth.
The important part being, all parties involved are working towards (and together) on a better faster more wonderful future.
Ember with another (faster) iteration if its rendering engine: https://github.com/tildeio/glimmer (written in TypeScript),
V8 with turbofan
and the team, working together to improve JavaScript in the browser for everyone.
