The real reason that Dynamic Queue is a problem is simple; it undermines competitive integrity.
I'm not high enough ranked to experience bad queue times because of it, and while certainly I've had some shitty premades none of them are really that bad. Matchmaking hasn't really seemed all that bad either (though I do believe its not as good as it was before this season).
The real problem is that an individual rank means nothing when you do not queue as an individual.
I have no reason to believe that a Silver 5 player is better as an individual player than a Bronze 5 one when that Silver 5 rank was achieved when he queued with friends. DuoQ in previous seasons was already pushing it, and many people were calling for DuoQ's removal long before Dynamic Queue was ever introduced. As long as rank isn't determined entirely by individual skill, rank means nothing.