Support for the monarchy is associated with older age groups [1]. Perhaps as time passes, those who are opposed or ambivalent will be in the majority. Maybe 40-50 years from now? I hope that William will try to get ahead of this, and persuade his father to lay the groundwork for the UK's monarchy to drift towards a different model. I obviously doubt he'll be in favour of abandoning the gravy train altogether.
[1] https://www.statista.com/statistics/863893/support-for-the-m...
Edit: Not sure about the people of the UK choosing for things to be "this way" by beheading Charles I. That was ostensibly a choice for constitutional monarchy instead of absolute, but developed into abolition of the monarchy. It was followed by the Restoration of the monarchy under Charles II, and I'm not sure that was much of a "choice" by the people either.
I think from KCIII onwards things will start to change as it becomes apparent that he and his descendants aren't really representative of the "the good old days".
Of course it's weird and strange and old fashioned, the entirety of the UK is built from the foundations on such things. Your love for brick over modern steel and glass, the countless centuries of history embedded into almost every location.
If this wasn't the case then I wouldn't have learnt so much as to why my life in New Zealand was so different to my one here.
But who knows, maybe people here really are ready to forgo all that, but from what I have seen so far I don't think so. Hell even the religious differences (NZ, it's not a huge part of our lives) are stark.