Whenever it is suggested that the concept of monarchy is outdated and a throwback to serfdom, someone points to Donald Trump as an example of what can happen if we had a presidency.
Why not point to past and present monarchs whose behaviour may not be considered to be very desirable? And I believe that in Thailand it is a crime to criticise the king.
The point is there are good and bad monarchs, as there are good and bad presidents.
However, I do believe that many older people in the UK (and overseas, as has been mentioned) have been conditioned to see our royal family as somehow superior to their "subjects", despite the fact that, generally speaking, they do not appear to be morally or intellectually better than the rest of us. I think their inbuilt privileged position in British society is totally incompatible with the concept of justice and equality. Though there are many examples of our system being far from equal and fair, to me the monarchy embodies the notion of inborn superiority.