Having low and stable inflation is helpful because it can create a more predictable investment climate. But beyond that effect, monetary policy doesn't have much effect on the feasible trend rate of growth. There are many drivers of long-run productivity growth, but monetary policy would be way down that long list. Its role is more in the short run than the long run.
Of course, there could also be synergies and linkages between the short run and the long run if there is path dependence. If short-run prosperity helps create the conditions for even more long-run prosperity, that is even more reason to ensure that policy supports growth. We are seeing an example of this in Japan at the moment.