I was going to ask the obvious question of why the Java ecosystem ended up differently than the JavaScript ecosystem, but I think I know the answer.
It's a giant pain in the ass to publish a Java library. That's already weeding out a ton of low-effort projects. By itself, I wouldn't exactly call that a good thing, but it seems to have a silver lining...
The same is not true for JS. The most mature libraries depend on absurdly vague libraries that no one has ever reviewed.