This is such a bad take. Getting in to the apprenticeship doesn't gaurantee you work. You have to look at the market in your area to see if there is work for the trade you are going in to. Schools and job posting can give you hints on this. You may have to move where the jobs are. It's a reality.
That union runs on a seniority priority for job call outs. Not all unions go by this, the one I was a part of gave priority to those who worked least the last 365 days. Don't paint the whole system as a scam.
Also my union didn't have contracts for callouts. The companies asked for X amount of guys, they go out for the duration the project. If they like you and there's more work available then they keep you instead of sending you back on the out of work list. But that's the nature of construction, it's up and down and you never know if you have a job after completing a project.
Apprenticeships work the same for non-union, but you have to look for more work yourself if you get let go, same as any other job in the world.
That's not how it happens in Canada. Private institutions run schooling and the government oversees the apprenticeship program. Unions don't have much say in it at all.