The UK could absolutely pursue some form of association with the EU if it so desired, it doesn't need to be in the EU for increased cooperation. The problem is that the UK people overseeing brexit wanted very much to cherry-pick only what was advantageous for the UK only and cede on nothing that the bloc desired.
As for Canada, we will have to wait and see. Is it a Switzerland style deal (an endless torrent of asterisks)? Is it something similar to EEA but lighter? Something that is more focused on trade and mutual defense and less on freedom of movement and financial ties?
Probably the main advantage of the EU is that it is much stronger at negotiating these sorts of agreements than any of its individual countries would have been.
It is a deal, both sides bring something to the table and try to negotiate what comes from that.
This reeks of being custom made to enrage one person in particular and give leeway for negotiations.
It's fanciful thinking to believe this is a slam dunk that could get done anytime soon.