This is cope - managers repeat this narrative so they can blame some other factor rather than having to put in the work to fix the problem of hiring good FTEs. Unfortunately, this narrative has been repeated so often that it is perceived to be axiomatic, which is why it is repeated without any criticism.
No, its not that hard to find good FTEs, you just haven't tried hard enough, or you're not paying enough, or your glassdoor reviews are bad.