If you're talking about Toronto and Ottawa, as far as I heard, a huge part of the reason is Downtown businesses are struggling now that way fewer people are commuting Downtown.
But the solution to this is not RTO. If your DOWNTOWN of all places isn't self sufficient I don't know what to tell you other than your municipal policies are failing. Just let people live in the office buildings. "Oh they're too wide and you'll have to make the units narrow strips that only have a tiny sliver of window on one side" Do that then. Tons of people would still live in those because Downtown should be the most desirable place to live.