As far as the deaths related to freezing temps and lack of provision for such conditions, to say that this is the central principle of the dislike of the NPZ is a gross oversimplification.
Those deaths were one symptom of a care paradigm that doesn't take into account the behavioural needs, biosecurity, health care, dietary needs etc. Etc. Covered by the worst kind of pseudoscience. It is almost a twisted parody of the rack 'em and stack 'em philosophy zoos took up until the 60's to shake free of.