> On the web or in the JS ecosystem?
I meant outside of your control on that device.
Are you claiming that even plain/styled HTML is too slow on these kinds of devices?
Sites like Hacker News and textual blogs work pretty fine if you get lucky and nothing is running in the background, but you have to wait for a while for the phone to stop crunching stuff. The scrolling has noticable latency and random hiccups. If you scroll too fast, the content will show up delayed.
Once you add some images or a bit of javascript, you start to feel a lot more jank. You often get a perf hit when you recieve push notifications or when you re-connect to wifi, or open a native keyboard accidentaly, same with triggering browser UI or tapping the back button. Also, the browser sometimes just crashes (I guess out of memory?).
It certainly is usable, but the latency variance of various actions is wild. Sometimes it feels ok to use, but other times the whole session is like 1 fps for 5 minutes.
On the web or in the JS ecosystem?
While I agree that even just the browsers are monster applications, usually duplicating (at least) the entire OS they are running on, just usually worse.
However, most browsers are perfectly capable of extremely snappy rendering and interactions, even on low-powered devices.
Let's remember that WWW.app was developed on a NeXT Cube, 25 MHz 68040, probably in the 16-64 MB RAM range (min was 8, but I am assuming it was more than the min), and that was plenty snappy.