There's a longer term issue that appears to be missing here. At what point do you change? There must be a point otherwise we'd all be here writing COBOL/CICS with some whizzy Javascript interface library. Over time it becomes harder and harder and more and more expensive to maintain old technology. Because frankly maintaining old technology is pretty boring and career destroying so you need to be paid more and more t…
I remember looking at Node when it first came out and got mildly excited, but that excitement quickly went away after writing a couple of small apps with it. It just wasn't for me. The same thing happened with Go. I didn't see enough wins to switch over to using either of them for building web apps.
On the other hand, for me Rails and Flask stood the test of time. Nowadays I'm working with Phoenix and I'm past the hype phase and it looks to be another winner. But in all 3 cases (Rails, Flask, Phoenix) I typically don't switch away from them for good. They just become another tool that I know. Of course I will gravitate towards the one I'm the most happy writing code with, but it's not a black / white progression from 1 to the other.
I don't think there's really a definitive answer on when to change. Like 3 weeks ago I picked up a Flask contract and it was a pleasant experience, even though I'm using Phoenix to build a side project currently. You don't always need to throw the old thing out. You can use multiple technologies in harmony. You change when you start dreading writing code in the old thing, which is very user specific. In other words, write more code and you'll quickly find out what you like and dislike.