Is there a continuous churn?
React is 10 years this year. Vue is 9 years. Angular which feels positively ancient is 7 years (if we only count Angular 2.x).
Yes, there are newcomers like Svelte and Solid, but it's hardly a churn. Besides, they explore valuable corners that are left untouched and unexplored by other frameworks. Things like granular reactivity and removing components as a unit of UI in its entirety.
Meanwhile the "non-churn" in web components has already resulted in two deprecated standards (custom elements v0, html imports), and is rapidly churning out dozens of new standards requiring more and more javascript to paper over their egregious design (form participation, constructible stylesheets, declarative shadow dom...)