> I answered that the modern web apps are very complex both on front-end and on back-end, and is hard to master both sides at same time. Instead of doing a little bit everything, one should be professional at one side and contribute the best of his knowledge.

You do need to be 'cross functional', you might prefer front end development, but you also need to be able to do back end development, and vice versa.

When you understand both, it will make you a much better developer.

And to quote Bill Gates, 'Measuring programming progress by lines of code is like measuring aircraft building progress by weight'

I'm sorry you lost your job but look at this as an opportunity to improve yourself and your skill set.