The last years of the Joe Dumars era were basically a disaster ("the AI experiment", Ben Gordon, Charlie V signings etc.). SVG took over a very unbalanced team (e.g. playing two centers) with poor chemistry.
I think he has done a decent job of bringing in some talent and balancing the roster, but there are still challenges.
Drummond is still just a yuuge pouting kid with no BBIQ and a poor motor. I doubt he will develop to the beast everyone was expecting, regardless of coach.
Jackson's blend of low BBIQ and selfishness is also a very bad combo. Hard to fix that for a coach.
Stanley Johnson hasn't developed at all (could possibly be on the coach)
KCP is a nice player but still inconsistent. You could put Morris in this category too.
I really cannot see this team becoming relevant any time soon. Trading Jackson would be a start.