I agree with you that the voting system is letting down Canadians, but I also think you are using an unfair framing with your "20%" figure which risks undermining the legitimacy of coalition governments (and thus efforts to introduce a more representative voting system where coalitions between smaller parties might become more common).
In particular, I want to point out that the NDP have agreed to help the Liberal government to pass its legislative agenda, which presumably includes this ban, as the NDP had pushed for a tax for non-resident home purchases, which is a similar policy.[0]
Considering the government as a two party coalition, therefore, and with the NDP getting close to half the number of votes as the Liberals, that would mean that 30% of Canadians voted for the current government. That's somewhere between Biden's numbers[1] and Boris Johnson's[2], to compare it to other major recent Western FPTP elections.
[0] https://www.theglobeandmail.com/business/article-ottawa-face...
[1] 34% = 81m / (158m / 66.2%)
[2] 29% = 14.0m / 47.6m