I'm a Brit-Pat living in Toronto, so didn't get educated the Canadian way, but I wonder if you were taught the same as us or differently on this point you made:

That Veto right is probably a single shot. A powerful enough government would eliminate the position immediately afterwards. That right still exists.<<

It's basically a type of emergency brake - The Queen can overthrow a PM that becomes a dictator, and the laws that came from the Magna Carta stop the Monarch also being a dictator. The Queen/Monarch is supposed to remain apolitical and allow the government to run things as it sees fit, however, as you rightly point out there is a power of veto - that brake was last pulled in 1708 by Queen Anne over the "Scottish Militia Bill".

That bill and the idea of an emergency brake neatly brings us to a modern example of what happens when you remove that brake. The US example of Jan 6th, shows that when an Elected President goes rogue, and the military is supposed to follow orders of it's Commander in Chief (the President), you're only minutes away from a potential coup. Under the Commonwealth system, the military is controlled by the Government, but has allegiance with the Monarch - meaning if Trudeau, for instance, went full-Trump and tried to do the same, every military of the Commonwealth would come help the Canadian Military to restore order under the Monarch.

Of course, this is all hypothetical since nobody has pulled that chain - but that's what is supposed to happen.