Prove what? That the monarchy and parliament are not very useful? hahaha
It would depend upon the definition of "useful". If you mean sucking up taxpayer money while contributing very little to public interest, then yes, they are useful for that.
The monarchy by itself costs about $50,000,000 per year and for what, spending on travels and ceremonies. The monarchy is one hell of an expensive figurehead and a soother for people who like the sentimental claptrap.
And parliament? It seems to spend most of its time catering to corporate concerns. The rest of the time is mostly spent on squabbling, scandals, stabbing the provinces in the backs, and generally being a leeching nuisance to Canadians.