Songwriters with the the best track record are still capable of writing some less memorable songs, if not indeed some complete 'turkeys'. A certain ex member of the Beatles springs to mind.

I know for example, of many of Randy Newman's great lyics, if not always the combination of words and music that make the best songs, but I do not hear of any of his 'turkeys'. Does he (or Dylan) not then write any?

I would suggest that individual songs, rather than their creators, are a more sensible means of inspiration. These songs can come from surprising sources, like writers in syles of music that you would not expect to be inspired by, or from a completly unknown writer.