No real superstars in their prime play in the Spengler cup, or prospects for that matter.
Don't underestimate the boys in Junior. They been holding their own amongst men.
CHL junior hockey is made up of predominately players who will never play pro hockey, in any league. i.e., in the AHL, KHL, Swiss League, Swedish Elite League.. The vast majority will end up in Canadian University hockey or stop playing altogether.
So I'm not sure how you can say that junior hockey is in any way comparable when most of the players in junior hockey will never actually play in most of the leagues you are saying are in some way comparable or inferior. That's before we even discuss that pro hockey players are bigger, stronger, and faster than players in junior hockey because they are, indeed, older, bigger, stronger, and faster. The jump from major junior (which is the best hockey in the world for that specific age group of players) to pro hockey in most leagues is substantial. The game is played differently. It is more nuanced but with tighter defensive systems. There isn't as much room to make plays, and they have to be made more quickly. It is more physical.