Buildings come and buildings go.
I see the logic in demolishing the existing science centre and building a new one on the Ontario Place property. We need housing. You're not going to build housing at Ontario Place, but you can build a new Science Centre and free up the land where the existin Science Centre is for housing.
The government can commission Moriama Architects to design the new state of the art science centre at Ontario Place. The firm still exists, run by his son.
I don't get the fascination with the OSC site at Don Mills and Eglinton because the land previously owned by Celestica is across the street. It is already being developed into housing and commercial space. Further, it is not in a ravine as the OSC is.
We certainly do need housing, but not at any cost. We also need cultural, education, natural and many other spaces because that's what makes a city vibrant. Would you want to live in a city that has no cultural, education or natural spaces whatsoever? Is there even 1 city in the world of Toronto's population that is like that?
If your argument is that we need to free up land at any cost, then there are large swaths of land we could target for housing. City parks including High Park, Centre Island, Leslie Street spit, golf courses, on-street parking and parking lots including those at TTC stations, Casa Loma, CNE grounds, the civic centres in Etobicoke, North York, etc, Nathan Phillips Square, Fort York, etc. Where would your list practically end?
How is the OSC property more suitable for housing while the OP site is not when both need extensive and costly construction? How is building a spa, casino, hotel, aquarium, ferris wheel, mega mall, undeground parking, or even a new science center justifiable in light of a housing crisis?
I do think that some of the land in Etobicoke Centennial Park could be put to better use including housing though I know there are issues with that. There are large portions of the park that sit empty and some of it cannot be accessed by people as there are no pathways. It is odd how Americans and Canadians created such huge parks that you need a car to travel within them. I do know that the park will be revitalized in the coming years though.
The irony with Centennial Park is that its ski hill used to be a garbage dump so some of the land might be unsuitable for housing. Who knows how the city monitors contamination levels if that's even an issue today.