> a 3'' device with 512MB RAM ... 2G
Such luxuries. I spent several years reading web pages on a 33MHz 386DX with 8MB of RAM. Yes, Netscape took a while to start (had to wait for the rest of Win 3.1 to swap out), and downloading images was always somewhere between "slow" and "don't bother" even with the glorious 14.4kbps of a fancy V.32bis modem[1]. However, it still only took a few (15-20) seconds to fetch an article and render it.
The slowness started when websites decided it was fashionable to add a few dozen unnecessary HTTP requests to fetch megabytes of Javascript. The bloat is self inflicted, and websites do not need Google's help to make their pages small and fast. Unfortunately, many pages value the bloated ad loaders and trackers, several types of spyware ("analytics"), and their favorite "framework" more than they value the actual content of the page or the reader's experience. Google is happy to pretend the problem isn't self-inflicted when it gives them more tracking data.
Yes, it's important to remember that there will always be a wide variation in the User Agent. That's one of the reasons well-designed websites progressively enhance the heavier features. Websites can do this on their own - just like they did 10/15/20 years ago. An over-engineered caching system isn't necessary. Do you want a future where the internet retains some of it's interactive, decentralized qualities? Or do you want a fancier version of Cable TV, mostly controlled by Google et al?
[1] On weekends I was stuck with the old 2400bps V.22bis hand-me-down.