On the one side: I get it. As a developer you want to - and the industry expect you to - keep learning, always be on the increase, etc.
But on the other hand, when you think about it, once the main architecture is put down and the main issues are solved, most software engineering jobs are just repeating the same trick over and over again, copy / paste / edit some names, done.
The last part is where you want to end up at as a company, basically; build features end to end in a reasonable time. But it's not what most developers want, they want new challenges, they want to stay in the problem solving domain.
I think as a developer you need to accept that a big chunk of your job, and what your employer wants you to do, is kinda boring. It's not solving new problems, it's extending the functionality of an application using existing solutions.
And if you're hired as a front-end developer or whatever, the hiring company may not want you for what you can become, but what you already are.
And honestly, just trying to find decent developers that don't need to learn your stack is already difficult enough.