I agree. The reason that I mentioned US is because there is a land border between them. For countries other than the US, if you want to return to canada, you need to board the plane, and without a passport, that doesn't seem to be possible. However, if a person shows up at a POE on the land border and claims to be a citizen/PR, even if a passport is not available, it is the officers' responsibility to verify that and decide whether to admit the person. I believe this was discussed in detail by @dpenabill in some threads.If you still want to attend your oath, you can ask the agent who will register you to expedite your certificate. I heard some people picked it up in person immediately after the oath pre-Omicron, and some received it 2-3 days after the oath by mail. But they may ask for a proof. The other option is to leave after the oath, and have someone mail it to you at your home country, and apply for the passport abroad. Keep in mind, if you have a job in Canada and want to return, this option may complicate things for you, because issuing the passport abroad in a local embassy may take months. Of course there is the last resort option to reschedule your oath until you return to re-enter Canada without any complications using your PR card.
Of course, this always creates more trouble than having a passport ready.