Websites get slower faster than browsers get faster. Interesting thread from Alex Russell on birdsite: https://twitter.com/slightlylate/status/996204502490337280
I think part of the problem is cargo-culting. Around 2006 everybody started doing Ajax because Google was doing it, and GMail and GMaps were amazing. But Google also employed some of the smartest webdevs on the planet, and not every organization had the know-how to get it right.
Today webdevs are busy React-ing All The Things because Facebook does it, without realizing that FB also uses machine learning to optimize their module delivery system, among dozens of other sophisticated techniques.
@nolan (In the sense that, something good (modularity, React et al.'s approach to webapps) was evangelized despite having high costs.)