(1) Drummond is strictly a garbage man on offense. Can't make a shot outside of five feet.
(2) Drummond has great physical tools defensively but is still fairly raw on that end of the floor. Probably a wee bit below average defensively.
(3) Tremendous rebounder
Right now, Drummond doesn't add enough in terms of offense and defense to warrant big minutes. He is in the right role in terms of minutes and responsibilities. Lawrence Frank is doing a good job of steadily bringing Drummond along. As Drummond's defense continues to improve, I'd expect his minutes to steadily rise.
Also, Drummond (C) + Monroe (PF) have serious spacing issues as a big man pairing which makes it difficult to get them longer minutes alongside one another. Monroe has a weak jump-shot and Drummond has no jump-shot.
Monroe needs to continue to develop his game offensively (jump-shooting, developing more of a power game in post instead of his current finesse post up game) and defensively (guarding further away from the basket both in man-to-man defense and team defense) to become a more able power forward on both ends of the court as much as Drummond needs to improve his own skill-level. Monroe's lack of refinement is just as large an issue here as Drummond's.
Also, Jason Maxiell is having a very good season for Detroit. An unsung hero. His best year since 2008 or 2009 whenever the last time was that Maxiell was a very good backup PF.
Charlie Villanueva gives them a different sort of weapon with his jump-shooting and explosive scoring. Detroit's big man rotation needs that (a big that can play away from the basket and space the floor for everyone) so Villanueva needs some minutes off the bench too.
All in all, I think Lawrence Frank is handling Drummond's role and minutes brilliantly. I think Frank deserves praise rather than criticism.