Interesting, because my company chosen Ember precisely because it would start a hiring wave of new developers, often junior ones. Mostly because of Ember's "convention over configuration".
I dont see much of this problem, including myself as one of these just hired jr devs.
The projects I work typically have very fast turn around times (2-4 months), so I don't have the time to teach a dev use a framework, and I definitely don't have the time to onboard junior developers.
I need a framework where any experienced JavaScript developer can pick up the project and deliver working product in a week. With Ember/Angular/React+Redux, I have to hunt for a developer that specializes in that particular framework. With Vue, the hiring pool is vastly larger.
I dont see much of this problem, including myself as one of these just hired jr devs.