I guarantee if you opened recruiting to folks applying to Immigrate to Canada as a "fast track' lane- even if it were a 3 year CE served and your family can be PRs while you're here, I imagine our recruiting problems would disappear overnight. Our ability to screen, train, feed, and house these troop are another entirely different issue though...
As for Ukraine, I'm certain they know what skill sets are needed at the front, because, well... they have a front they're trying to maintain. I doubt their recruits are put through the same paces as our troops, as we recruit with the belief we're going to have this person go the distance to IE25. Ukrainians expect these troops will all go back to civilian life once the Russians are defeated. They want to have their doctors, engineers, service industry workers, teachers, welders, etc. all back on the job to rebuild their society.