Sorry, I should have qualified it as Single Page Applications, not web apps in general. Still, hard to find a front-end job that isn't about SPA anyways.
There are learning curves, inner platform effect (have to do the framework way of doing things), major breaking changes and outdated information, opinionated authors you may not agree with, huge dependencies for users to download, performance bottlenecks and gotchas arising from not using the framework properly or even the framework itself is slow. These things are basically guaranteed.