If someone writing a novel has to look up the spelling of a particularly useful word that fits the situation perfectly, but they can never manage to spell it right without aid, does that make them an impostor?

No brain can contain the exact right way to do x, y and z - and it needn't, because we have a magic box that we can ask and get great help when we need it.

IMO, being a developer isn't about being 100% amazing with your syntax or being able to recite the ES2015 spec by heart; it's about knowing what tools to use when.