[cjblomqvist]

Having been fairly close to the Derby.js project I'd guess that the difference between it and just using React and a web API just isn't that much in reality. Live updates of data isn't something most applications need (and very few parts of those that actually do). The added complexity is not to be underestimated, and there are some things inherit with live data which makes it more complex. What happens when one piece of data updates at an unexpected point in data, half-way through a method where you process something? Plus you still have the difference between backend and frontend, just that now it's more difficult to understand where and when what is run where under what conditions.

Then specifically for Derby/Share JS they didn't put enough resources into the project to make it good enough compared to the alternatives.