Whether the addition of BPK has been a net positive or negative for existing owners will differ from owner to owner. If you have no interest in studios or reject anything without a full fridge, then yes, the change is negative (although I'm pretty sure that full fridges could be added, if the demand for this is really there). Others do benefit from an increased inventory and quite beautiful studios in a great location. I'm personally mostly interested in studios while I'm at WDW.
But things will never stay the same and most changes will have some negative consequences. When Poly2 opens, whether it joins the existing association or not, it will probably get significantly harder to get on the monorail from GF to MK. I guess people owning at BLT were annoyed when VGF opened and there were more people on the monorail going to the TTC.
I really don't see the addition of BPK as this dramatic change. I'm sure, that DVC owners had other things to complain about before that.