For most people, the intuitive thing is to look to successful companies: Google, Facebook, etc. The problem here is two fold: (1) operating at scale often has requirements that supercede making individual pages fast for individual visitors and (2) massive market dominance/semi-monopolies/vendor-lock-ins means these companies don't really need to compete on perf. See Facebook.com/gmail.com as lovely examples of some of the worst performance on the web.
You're right that one can make a webpage fast with correctly implemented js, but I disagree that people can make webpages fast en masse with correctly implemented js; dissuading the use of JS is much more likely to have a positive effect than expecting people to somehow spontaneously learn how to write good js.
Developers seem to have forgotten progressive enhancement entirely and just piled more and more JS in to the first page load. Consequently users complain about JS, but JS itself is not the problem. There are patterns for building websites that are fast, in terms of both literal download and rendering speed and the perceived speed the user feels. We 'just' need better developers who actually care about the sites they build.