Im not quite sure about the majority, but in my small community, the problem with GDKP is that is becomes all about the gold. Instead of raids being gathered around by people needing gear or people hunting a specific upgrade, the LFG is filled with BiS people, who are looking for money bags they can carry through Naxx and then have them pay for the gear when it is done.
Its about it looking like a different form of boosting.
Its about it taking over the raid scene and reducing the number of "normal" raids where the focus should be on gearing.
Its about the redirection of requirements from raids going to "How much gold do you have" instead of "What is your experience, gear and class/spec".
I don't agree with all of these statements, but it is what the broad opinion seems to be when i talk to people about it.