I think that if someone knows how to write a web application from scratch, using only libraries, then they can easily pick up and learn a new web framework. (Well, I guess 'easily' is relative. Some of those frameworks have quite a learning curve, even for an experienced coder).
However, if a young developer learns web development using a framework, and then moves on to a new project where that framework isn't in use, then he/she needs to either learn a new framework, or actually learn how to code without relying on a framework. How to manage state? How to manage history? How to manage binding? Frameworks have implemented a lot of the boilerplate code to do these things, but they all do them differently.
However, one of my biggest hangups about web frameworks is their transient nature. What happens to that big enterprise project five or ten years from now when FrameworkX has gone out of style and no one knows it or wants to work on it anymore?
How many devs are out there struggling to maintain a big Angular.js application written five or more years ago, which was too big and complicated to convert when version 2 came out, and besides there was no compelling business case for management to allow for a conversion effort?
Now the rest of the world has moved on to the completely rewritten, new and improved Angular, and the company has to try to find developers willing to work on an old, out-of-date framework that no one wants to work on. I suppose this isn't so different from other frameworks of the past, but at least they had a longer shelf life (e.g., ASP WebForms).
And how does one find decent documentation when the frameworks change so fast the documentation can't keep up?
And please don't get me started on the thousands of dependencies these frameworks rely on. It seems to me like a house of cards ready to fall.
I get the arguments about standardization, etc. But that argument only holds so much water. The standards change so fast that the word barely has any meaning.
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