Android 4.1-3 are from 2012, early 2013. So 6-7 years old. Those old devices are barely functional to view modern webpages, anyway.

That’s the assumption I made but is that actually true you think? This is true of iOS devices after OS upgrades, I’ve experienced this myself: Apple ruins old devices with software updates. But I somehow doubt that a phone from 2012 must be ruined with bad software. Any idea?

Not bad software, underpowered mobile device CPUs. Mobile CPUs have only started stabilizing around "good enough" around late 2016 and that was for flagships (with Snapdragon 820, basically).

A mid range Android phone CPU will choke quite hard on modern Javascript-heavy web pages. Now think about a low range phone...

I don’t know, older Androids take 4-5 seconds to parse my webpack bundle. That’s not too bad for these devices, given that once it’s all parsed and evaluated, the app seems to work fine. I do want to buy some even older devices to see how they run. With webpack and a little effort, ares these older phones really bricks?

We still support Android 4.1, iOS7, and IE9 because our users don't choose to use our web app (their company does). There are low income users in our demographic for whom spending money to upgrade their phone is not their priority.

With care it is possible to make mobile web apps run at a reasonable speed even on low end devices. I personally like to aim to make things work OK on shitty old devices, that way I know it works well on newer devices. Also our code (custom) was originally written for IE6 so we started light, which helped.

A framework that appears to be good on low end devices is svelte.dev: "Last month, a developer in Brazil shared that [Svelte is] being used for point of sale systems in Brazil. There are like 200,000 of these devices in the wild. His job is to build this interface for the point of sale system. They're working with a very outdated version of WebKit on extremely memory constrained and performance constrained hardware. They tried a dozen different frameworks and none of them were up to the task. You would press a button on this interface and, half a second later, it would respond, which is kind of an awful user experience because you're more likely to press that button twice and end up overcharging your customers or something like that. They tried it with Svelte and it worked smoothly, so that is an example of what you can do when you have a framework that has a very, very low memory footprint and very good performance. Another example, we have a guy using it in the context of smart televisions, which also tend to be quite constrained devices." From: https://shoptalkshow.com/episodes/349/

I’m excited to try Svelte. Looks great.

hopefully firefox will continue to run fine on those (and get faster over time)

chrome on android is dead to me. so many antifeatures it's maddening.