Learning something new is your responsibility and not necessarily your employer's. If your current job hasn't offered the opportunity for you to learn then you're either not looking for for them, not pushing your boundaries far enough or need a new job.
You'll need to go back (in your mind) and look at the project(s) you worked on during that period and see if there was an opportunity that you missed to push your comfort level. Could you have done something different to have changed that? If you can answer yes to either, then it's not your job, it's you. You'll need to actively look for those opportunities more carefully as the project unfolds.
If you can honestly say that there were no opportunities to grow and learn in that period, then it's time to move on.