The problem is that the original paradigms were pretty terrible but JS has to keep (as much as reasonably possible) backwards compatibility to not break the web. If you forked JS and made changes to clean it up that weren't backwards compatible, you'd have a hard time convincing browsers to take it, making the whole exercise sort of moot.

The fact that we have things like the Wayback Machine is a testament to how this approach, while terrible for developers starting out or working in a legacy codebase, has enabled us to preserve what is now a significant portion of contemporary cultural history. AFAIK there is no similar archive of programs for, say, Java or C.