Canada

And another thing: we often complain about not having enough density, but having too much density in a small, single area can be a major problem too. So while this might be controversial (not to mention unrealistic), I really wish we could reduce the skyscrapers. They're just unnecessarily tall and concentrate far too much in too small of an area[1].

But if you walk around most major European cities like Amsterdam, The Hague, Munich, Milan, Copenhagen, Stockholm, etc. you don't see gigantic skylines or massive skyscrapers. You see endless roads with dense, multi-level housing (3-5 stories), and plenty of mixed-use space. It makes cities more spread out, but still dense enough to have a useful public transit system. More schools, more parks, more commercial space (and more diverse uses of commercial space too).

Oh well, I can dream...

[1]: While there are some residential buildings over 300m tall, most them are concentrated in supercities like New York, Dubai, Moscow, and various Chinese/other Asian cities and require much larger populations than you have in most other major cities in Canada/North America.

Unfortunately a lot of office towers are unsuitable to be converted into housing.

How much is "a lot"? I've seen several retrofit projects that seemed incredibly challenging take off and be successful, so I don't really know if there are really that many buildings downtown that would be terminally unsuitable. Specially given the somewhat uninspired and homogenous trend of glass towers, and the wild income potential of rentals in downtown.

It's also quite difficult running plumbing and other services in a building not designed for it.