Education is one factor. A diversity of power structures is another. America wouldn’t be in the state it was if the monarchy needed to approve supreme court appointments.

The monarchy didn’t stop the UK from being taken out of the EU, that was a referendum and they’d bring out the guillotines of the monarchs tried to override that. The monarchy doesn’t need to actually intervene to be effective at maintaining stability, the threat of intervention is enough to keep the far-right from trying to overthrow or corrupt elections.

I think the UK system of the hereditary lords in the house of lords is better than the monarchy. A inherited position sitting at the back of democracy that can delay legislation should it be the result of blatant self-interest or populism. The house of lords is closer to a group of average upper class people with clear limits on their role.