JavaScript Fatigue Strikes Back
I think is a nice very high overview of the current state of the Javascript ecosystem.
I also like this potential explanation for why there tends to be more churn than with backend frameworks:
The problem was that, unlike Ruby, PHP, or Python, most JavaScript needs to run in the browser. Historically, this put an evolutionary pressure on JavaScript frameworks to be small and bereft of legacy code, rather than expansive and featureful.