Yeah and if you visit a site everyday, the JS is cached, too. After the initial download, it shouln't be an issue. This is besides the fact that it should not take MBs of JS to make complex applications.
The issue is what people are choosing to do with the tools, not the tools themselves.
HTML can be cached, too. Even if JavaScript permitted some clever way to safe network traffic like for example delivering the site as a torrent that is then downloaded from other visitors [0], then we can standardize that and implement it as a part of HTML or so.
Except that the current trend in webdev is to deploy small incremental changes multiple times per day and cache-bust the assets that change on each of those deploys. So the user is probably actually downloading the JS asset at least once per day Monday through Thursday (because no deploys on Fridays).
Well right now the problem is that the tool is broken. We have a long term non fixable issue (outside of replacing the hardware) with non trusted code running locally.
The issue is what people are choosing to do with the tools, not the tools themselves.