I think it's more about recruitment. I can make the case he's developed talent pretty well. Here's who improved over the course of their careers under Martin or played their best season under him: Jordan Barnett, Kassius Robertson, Jordan Geist, Mitchell Smith, Reed Nikko, Xavier Pinson. Jontay Porter was in position to have a great sophomore year before the injury.
On the flip side, Tilmon stands out as someone whose production hasn't taken off like you'd expect, but he's got one more year to leave his mark. Pickett, Watson and Mark Smith either stalled or went backward last year. Injuries have dogged Smith the last two years.
So, I contend more players have improved under Martin's watch than haven't. The shortage of elite talent - the kind of players who can carry a program for stretches in a game or for a month - is more of an issue, in my opinion.
Plus, the injuries. We can't discount the minutes missed by Porter (both of them), Tilmon and Smith.