It doesn't help that ~every mobile device is 6+ cores while the web still largely pretends that there's only a single CPU core & that that core is getting faste

It doesn't help that ~every mobile device is 6+ cores while the web still largely pretends that there's only a single CPU core & that that core is getting faster. The web should have started adapting back in 2006 when this trend really become common reality, but it didn't. So you're stuck with 1 shitty CPU core, and you're stuck sharing it with the browser & JS runtime (yes there's of course multithreaded aspects to the browser itself, but you're still sharing an awful lot of CPU time on your single thread with the browser). 1/6th to 1/8th the performance of the phone is the most you can achieve if you're lucky. That's a fucking terrible starting point, and nobody should be surprised the mobile web sucks ass as a result.