“It is a rule, almost without exception, that writers and painters, who are always talking about being artists, break down at just that level.”
Anthony Powell, A Writer’s Notebook
Yes, it does seem to be common that writers who talk about being writers generally aren't writing. The writers who talk about structural problems they're trying to solve and whether their solutions are congruent with the characters they have? Those are actual writers.
And the axiom about how writing about music is like dancing about architecture? Polemical fluff.