I think you are correct in that you don't need to know everything to get started. But it also shows the benefits of maturity of the technology stack. As much as I would love to develop my geospatial analytics app in Clojure...I'm doing it in Python/GeoDjango. And unlike my attempt in Clojure, it is going incredibly smoothly. The language bugs me, but it is better than tracking down bugs due to the immaturity of the ecosystem.