This is a cogent argument for having a ceremonial and practical/executive head of state, but doesn't even touch on why a hereditary monarch is in any way superior to having a ceremonial President and executive Prime Minister, as is common in other countries.
The monarch plainly has no legitimacy whatsoever, there's no merit, nobody elected them, they were born into the job.
In contrast an elected President can use the ceremonial position to seize actual power. This isn't even just theoretical, it's an actual problem - or I guess if you've just used it to seize power, a brilliant feature...
Anyway, we don't want that, so the monarch is better.
