I agree with this perspective. Every idea can't be curing cancer, and many innovative ideas are stumbled on while playing with something else - like Feynman discovering quantum electrodynamics because he was curious about why spinning plates wobble. You need to follow your instincts.
At a minimum, you're providing a service to thousands of people and sheparding a product through its lifecycle. I don't know if working on Twicsy will have any real influence on your future work, but following its story seems more valuable than dropping it to "pivot" off in some random trajectory.