>Try loading up a library heavy site (i.e. React plus a half dozen associated helpers for state, UI and whatever, which is pretty common) on an old or cheap Android device.
that was the case in 2015 when entry level android devices were quite slow, nowdays a cheap $200 android phone has at least 4-6GB of RAM and an eight core processor.
if that isn't enough for your react powered site, you are doing something very wrong.
Keep in mind that React is very single threaded (as is nearly everything in javascript). These phones might have 8 cores; but they tend to have the same single thread performance as 10+ year old iPhones.
The performance of client-side web applications asymptotically approaches load times of "at most a few hundred milliseconds" on the high end phone models owned by developers.
Which react sites? Are you sure you are not a victim of confirmation bias? How often do you check what framework does a smooth and performance website uses?
Because demo sites are snappy on even low-end devices. It's not react itself that causes slowness, but all the other libraries/tracking/ads.
Which (correctly) doesn't even have react listed, only frameworks that (may) use react as a library.
So at least be specific what is problematic, is it a particular framework, a particular library, the whole idea behind react (v=f(s)) or what? Anything can be proven against something non-concrete.
that was the case in 2015 when entry level android devices were quite slow, nowdays a cheap $200 android phone has at least 4-6GB of RAM and an eight core processor.
if that isn't enough for your react powered site, you are doing something very wrong.