Well I think this is totally misleading. Here are some statistics,
Between Feb 22 to Mar 06 (since the rule was implemented),
Total number of Positive COVID cases in Canada:
27,273
Total number of Positive COVID cases from Travelers (Both Air/Land):
267
So only
0.97% of COVID cases that were identified in this period were with travelers to Canada, which would have been still mitigated if the travelers were in a 14 day home quarantine. An important point to note, it is mandatory for almost every traveler to undergo testing. But it isn't mandatory for the general public to do so, hence the 27K number must be much higher. If someone follows news regularly they must know the fact that every strand of COVID known to mankind is already doing circles
within Canada
Sources:
For Travelers:
https://toronto.citynews.ca/2021/03/12/travellers-covid-19-health-canada
For Canada:
https://www.ctvnews.ca/health/coronavirus/tracking-every-case-of-covid-19-in-canada-1.4852102 (Which is replicated to Worldometer)