The problem with Closure is that it really sucks for small projects. It was built for large products with hundreds of developers and millions of users; many of the library features (eg. static typing; dependency management; compilation; CSS renaming; namespacing & scoping; full component libraries) are absolutely invaluable for that use case, but don't get you much when you're just prototyping a few ideas. I don't think Google's webapps could run on any framework but Closure, but when I and many of my coworkers want to do a quick prototype, we reach for JQuery or Angular. Or even just native DOM APIs.

All big projects have to start out as small projects first, and so most small projects. If a small project uses a framework that's great for big projects, they're paying all the overhead for that up-front, which puts them at a disadvantage in the marketplace. I could see Closure being quite useful for rewrites, but once a dev is in charge of rewriting a project with dozens of devs and hundreds of thousands of users, he probably doesn't have time to blog about the latest JS framework.