Canada has the fiscal capacity to spend as much (temporarily) as 4% of GDP on defence IF, but only if, there is the political will.
I am 99.9% certain that political will does NOT exist.
Both the Liberals and their Conservatives poll assiduously for their own, private, internal purposes. They both hear exactly the same things from almost all Canadians:
There is NO serious military threat to Canada - thus there is no need to beef up our defences;
IF a threat suddenly, unexpectedly materializes then the USA will protect us - we have a deal, don't we?
The economy, the climate, health care and crime are all high on Canadians' agendas - defence is not.
There are reasons why Pierre Poilievre is not banging the defence spending drum; not even one seat, anywhere in Canada, will turn on that issue.