A 'dense version of sprawl' is actually more conducive to urbanity than our current sprawl - when a certain density of people exists, it can support everyday services within a walkable radius (shops, schools, transit, etc.) which leads to the street life we commonly associate with urban neighbourhoods.
The problem with the way we currently do sprawl is that the density (and often the lack of direct walking routes) requires everything to be too far for you to walk to. It also means that reliable transit service is difficult to justify. So, the automobile becomes the only real way to get around.
That then leads to lower densities (because of the high space requirements for roads and parking), even less walkability, a breakdown in casual social relationships, a retreat from and the breakdown of the civic sphere, etc. until we end up with the lifeless, dull and isolating fields we call the
Automobile Suburb.
The existence of a city doesn't require the existence of this specific kind of suburb. Far from it - their existence puts enormous strain on the city which, by the fact that it is urban, cannot geometrically (or financially) handle the influx of cars from the automobile suburbs. But the best way I could illustrate my point is that cities existed long before there were Pickerings and Lavals and they did quite well for themselves.
That's not to say that you could nuke the 905 tomorrow and Toronto would get along just fine (it wouldn't), but we need to get over this ridiculous fetish for the segregation of uses (like CBD - Bedroom suburb, in this case) and start conceiving of and building our cities with varying levels of urbanity, but with a minimum threshold at which walkability (i.e urbanity) can be achieved.
Leslieville, Toronto. An example of a good 'minimum urban density'