This is simply untrue, unless you consider all of the Golden Horseshoe the GTA.
There is a crazy amount of construction in Kitchener, Waterloo, Hamilton, Niagara, Barrie, Cambridge, plus considerable intensification (but not skyscrapers) in places like Guelph, Brantford, St. Catharines, Ottawa and London. The whole of Ontario is experiencing a massive amount of construction.
Beyond Ontario, Edmonton and Calargary are seeing plenty of development, so is Halifax. Skyscrapers are not everything and there are housing booms across the country.