I think this is a reasonable assessment, and I say this as a Monte fan. Monte was not dealt the best of hands, and did have some bad luck (the failed Bogdan/Buddy trades, which were largely not his fault). At the end of it, what matters is what the record says.
Clearly, he came in with a mandate to try and make the PO, so a full scale house cleaning was not really an option. How much did that impact his desire/ability to trade folks like Barnes, Holmes or Bagley will never really be known. I am not saying these folks should have been traded for pennies on the dollar, but in the absence of any information, we have no idea if he tried to trade them and if the market was cold, or if he thought they could increase their value.
He has a decent draft record, and has not made any BAD moves, which is equally important. Jury is still out on Davion, though the end of the season was quite promising.
One constant issue is that we don't seem to be able to find value picks. Most other teams, particularly the good ones, will have low draft picks, players signed on the cheap, throw ins from trades, suddenly flourish, and help the team consistently. We probably haven't had a second round success since IT (please correct me if I am wrong). Most of our FAs have played below their historical (and contract) value. Holmes is the only player I can think of who has outperformed expectations when we brought him in. Barnes has been solid, but I think we expected that of him. TD might still make a case, but we have to see a larger sample.
A lot of it happened before Monte took over, so it's not all on him. Perhaps it's the organization, or Luke over the last few years, or something else. I don't know. When we were good though, we consistently found great players with low picks (Peja, Hedo, GW, Martin, even Cisco. Including Peja here, even though he was a lottery pick, but pretty late lottery). Was it drafting, the coaching staff, or the general organization then that allowed these players to flourish? Perhaps a little bit of everything. Point being, it might not all be Monte, but he's the one who gets the credit/blame.