Although I'm ideologically more of a republican, I've come around (especially after four years of Trump) that it's no coincidence that constitutional monarchies are the most stable and prosperous countries in the world.
To paraphrase Heinlein in The Moon is a Harsh Mistress, the problem with democracy is that you have to expend a lot of effort with the reward being power, and so politics usually attracts power hungry people. In a presidential system, the power hunger of the president is kept in check only by other people with a hunger for power, which will ultimately lead to a positive feedback loop and could quickly slide into a dictatorship. The USA came dangerously close with Senate Republicans not wanting to control the power of the executive branch, but are ultimately only the latest step of ever increasing power for the president. Next time they might not be so lucky.
Conversely, in a monarchy, the highest power does not necessarily want it. In fact, there's some argument that the whole being born into a life as a ceremonial circus chimp actively deters them from it. The fact that the average monarch reigns for forty years also makes it resistant to populism.
Moreover, it works as a real check for power hungry politicians in two important areas, and I think the latest season of the Crown highlights this well with Thatcher ultimately being subservient.
1) the theoretical highest position is simply unobtainable for wannabe despots. Can't even think about it.
2) every time, and I think this is very important psychologically, the Prime Minister (or even the legislative branch) wants to get something big done, they need to request an audience with the monarch and bow and curtsey all the way up a long flight of stairs and past palace employees looking down on them. Yes it's ceremonial but it's still humbling.
