If she had wanted to, at some point, abdicate in favour of Charles, that could have been arranged. It would have required a special Act of the UK Parliament (following the prior example of His Majesty's Declaration of Abdication Act 1936) [0] – and probably also supporting legislation in the other Commonwealth Realms (Australia, Canada, New Zealand, etc) – but no doubt the governments of the Commonwealth Realms would have obliged. It was her own decision that she did not want that. I would not be surprised if, in another 10 or 15 years, King Charles III makes a different decision, but we shall see. In recent years, monarchs abdicating due to advanced age has become rather common – the Netherlands, Belgium, Spain, Luxembourg, Japan, among others.
[0] http://www.bailii.org/uk/legis/num_act/1936/ukpga_19360003_e...
(Spain is somewhat of an exception, but Juan Carlos' abdication was linked to corruption allegations over shady business dealings in Saudi Arabia; I very much doubt Elizabeth had any such skeletons lurking in her closets.)
So, if the Dutch monarchy can survive it, why not the British? I think you are probably right about her own attitudes to the topic, likely irreversibly marked by the events of 1936. But I'd be surprised if the same is true of her son or grandson.
The damage in both cases were mainly to their pride. If that was all she risked, I'm not impressed. Her uncle Edward was a literal Nazi, and yet even he was willing to give up power to marry the woman he loved.
But it could of course be that she risked more than that. What keeps elderly rulers clinging to power is often the knowledge that they and their close ones has done some very bad things, and that the descent may not be so graceful if they let go willingly.
Her son and heir has literally been accepting suitcases full of cash from middle east despots (nominally for his charity), and her other son was up to his neck in Epstein's dealings. I wouldn't be so sure.
Note that this scenario may still happen, but she was extremely lucid to realize its salience:
https://time.com/6212004/queen-elizabeth-republicanism-anti-...