Hoover didn't investigate the Mafia you know why? Because he knew he didn't have any fucking room to talk he was even worse than the Mafia. Him and the entire FBI.

Anyway, back to the question, yes it hurt the mob look at how many Families just went extinct due to not inducting new members. People talk about how successful and low-key the smaller Families were, but what good was it if they no longer exist? The proof is in the pudding, Families that continued recruiting are still here today. How strong or weak they are is completely beside the point, as long as there's still a presence they can always regain strength.