Long established procedures are often very difficult and very tedious to change, few countries carry out such tasks unless they are very necessary or they have been defeated in war or something. Germany has a modern Government because they had a clean slate to work on.

Canada, like America with it's Electoral Collage, or Britain with it's House of Lords, would probably need a very good reason to go through all the expense and work of rewriting it's Constitution and haggling over details.

Why would they want to? I think they could form a new type of government if they wanted to. The Queen is only titular head of the country.