Terrible infrastructure is a bit of a self fulfilling prophecy here. If you've only ever built it out to places that already have density, there won't be places without density almost by definition unless something like Detroit has happened in the meantime.
There's certainly land within close proximity to Toronto that could be used if there were political will. Georgetown is closer than Bletchley Park and already has a (terrible) train connection. Nobleton is like 10km from Vaughan, well within easy reach.
If you look at other Canadian cities there are even easier wins. Calgary has empty land (not parks, not reservation) within 8km of downtown. Winnipeg is practically a model city for this kind of treatment. Vancouver and Montreal are the only obviously difficult ones due to their geography.
But it's still sprawl. Yes, there's cities that can still sprawl more, but building sprawl is not the same thing as building a new city. You're just building a place for people to sleep while they work somewhere else.
You have to build something self sustaining and that requires jobs in the new city. You can't just have a connection to an existing city. You need an industry or institution or something there to attract workers and the workers to support those workers.
There's certainly land within close proximity to Toronto that could be used if there were political will. Georgetown is closer than Bletchley Park and already has a (terrible) train connection. Nobleton is like 10km from Vaughan, well within easy reach.
If you look at other Canadian cities there are even easier wins. Calgary has empty land (not parks, not reservation) within 8km of downtown. Winnipeg is practically a model city for this kind of treatment. Vancouver and Montreal are the only obviously difficult ones due to their geography.