To answer that question one probably needs to ask who's to say how great it was and when, or at least who was there to say over the years?
In my opinion, ANGC became great, really great, when it was designed and constructed and opened.
From there it may've begun to devolve down and away from greatness---or at least from its inherent architectural uniquenes, to some ongoing degree.
I'm beginning to feel in concept, if perhaps not in execution in an enduring way, ANGC just may be the most important golf course ever done simply because it was conceived to be an accumulation of incredibly interesting design ideas that noone else had thought of or attempted.
The irony is it may've been largely misunderstood or a casuality of other somewhat unrelated factors.