Carney is pursuing what he calls "associate membership", which has yet to be defined[1]. If the EU wants to form the backbone of a group of middle powers that can hold their own against superpowers like China, as Carney has suggested in the past, they are motivated to offer a deal that doesn't include unacceptable loss of sovereignty. If they can do that, other nations might follow Canada's lead.

One thing the EU has not done is threaten to use economic coercion to force annexation, as the U.S. has done repeatedly. If becoming an associate member of the EU involves some loss of sovereignty, it will probably be less than we'd surrender by choosing not to diversify our trade away from the U.S..

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[1]https://www.reuters.com/world/americas/carney-pushes-idea-ma...

“This power bloc is actively trying to take our sovereignty, but conspiracy theorists say the other power bloc will do that and become a superstate, so we’d better stick with the one whose leader has literally threatened to invade us” would be a weird take for Canada.

No-one’s talking about Canada joining the EU. And ah, leaving the EU is fairly obviously possible; see the UK.