I think the major factor is the cost.
Since the privatisation of BK parking fees and rent has increased disproportionately to the CPI. This ultimately has to be passed on to the customer.
The same situation has occurred in CB when it was privatised. It decimated the number of flying schools there.
Another factor is the decline in aviation in Australia.
It seems to me that people would are only prepared to invest the necessary money required to obtain a CPL if they were reasonably certain that a good flying job would follow.
There are many who are not prepared to outlay money, complete the training and then to face the prospects of having to head north and having to stack shelves in supermarkets, pull beers in pubs in order to scratch out a living until perhaps stumbling into a flying job that pays stuff all. They want jets with 200hrs TT!!!
As for the airspace, NAS IS inherently less safe than the previous airspace. This is not the place to go through the 'why's' etc - this subject has been flogged to death on PPrune. Whether it is a cause for the downturn, I don't know and cannot comment. However, it seems to me a bit early to say in light of what I have said above.
I'm not sure that a roll back would confuse pilots either. You have to have some modicum of intelligence to be a pilot, and that requires an understanding of the airspace we intend to fly in on any particular day. If the changes to airspace caused confusion, why don't we get rid of NOTAMS (which can effectively do the same thing anyway)?