My point wasn't that there aren't interesting tools younger than 6 months, just that nothing compels JS devs to use them or even pay attention to them until they're as established (in age, use, GitHub stars, whatever) as is comfortable for them.
The churn in tooling is unavoidable even if you use slightly less fashionable frameworks.
I'm not claiming that all those transitions were for the best, far from it, but the real question for any language community to answer is: "how much churn is acceptable in the pursuit of better?" JS is an ongoing cultural experiment in seeing what happens when you turn that dial to 11.
And realistically speaking, yarn is not a discernable improvement over npm.
The cultural experiment has a huge cost to programmers and it's been an utter disaster. Even PHP has leapfrogged javascript.