The Mayor needs to ask the Billionaires and other wealthy people in Toronto to pony up and partially fund this. That's how Millennium Park was funded through private channels.
Otherwise, we have no choice but to accept a slimmed down version of the park with condos.
Some of the billionaires are already contributing significantly to many other things around the city, so I'm not sure why they alone would have to be responsible for a park that would cost almost two-billion dollars (and which can't be built anyway now).
The whole city is not considered park-deficient; this particular portion of the downtown is. It is, and always has been, a difficult argument to suggest such a massive expenditure for just a park. In my opinion, the city and the applicant should have looked at working together at some form of joint effort that could have resulted in some kind of development and the retention of a significant area for green space. Instead, we ended up with conflict.
The critique that the applicants plans are not good because the increased heights of the area to accommodate parking is not conclusive. That's like saying you can't a have a park with a hill. Why would a multi-metre change in height be worse than some sort of a flat slab? It could be a unique and attractive feature. The idea should be to remain open to something unique and creative, all the while enabling development that could accommodate or underwrite part of the cost of this effort.
Regardless of the outcome, the development of this site will likely be a long time coming. And while a park was the hoped-for outcome by many, given the complaints of how the city actually manages and maintains these green spaces, a park-only effort was not necessarily a huge confidence-builder. Obviously a larger-portion of the cost is almost all on the structure. Should that have resulted in cost-overruns, the "park" might have ended up being a glorified grassed-over slab. At nearly two-billion in city funds, politicians would have a lot of answering to do to the taxpayers who had to pay for it. And some people were calling for a tax increase to do just that.
I know there is an idea floating around that this has been nothing more than a site-flipping exercise carried out by the applicant to drive up the price of the location, but that remains to be seen. The LPAT exercise did show that the venture would require a lot of players with serious capital and experience in this type of development, so who knows, maybe they are very interested in moving on this.
In the end, it is very likely that the only way to get this area decked over with some green space on it will be to include some significant development.