A supposed "top" program keeping a coach for 30 years who never won a championship would say more about the program's acceptance of second-tier status and lowered expectations than it would say about a coach being part of its lore. To me, being better than average for a very long time doesn't make a coach worthy of exaltation at a top program--even with these lowered expectations. You have to conquer the mountain sometime to prove that you're elite.
But as I said, there' nothing that says they can't make a statue for better-than-average. And there again we would see strong evidence of lowered expectations.