I wouldn't call it a bad sign. Backbone was the first JavaScript framework to gain a lot of traction but quickly stagnated. Release dates are few and far between, it doesn't change, it doesn't evolve, etc. On a positive note, it did pave a road for Ember, Angular, React, and others.

I would argue that it doesn't exactly need to innovate, since it's supposed to be a minimal way to make a SPA. If you do want more complexity, there's always Marionette: http://marionettejs.com/

If not innovate, at least keep up. Frameworks like Marionette don't instill much more confidence since they're based off a stagnated library.