Oh, I see. I haven’t seen / heard any talk about it.
I guess maybe some tourists will not bother to travel to UK for a particular Royal event, such as a Coronation or a Jubilee Celebration when Charles is King, if they don’t hold him in the same high esteem as Elizabeth II is held around the world, but I can’t see it making much of a dent in the number of tourists who want to come for general tours for the history and culture, the Royal Palaces etc - the Covid pandemic has already scuppered visitor numbers so much, it would be difficult to make comparisons for quite a few years to come until things settle down a bit, though.
I used to live in a tourist town and used to serve and chat to many tourists from around the world. I got the impression that most of the appeal to tourists was the things you have listed.
The sights that visitors see at the Tower of London, Windsor and Buckingham Palace are more about the traditions, history, pomp and ceremony surrounding the Royal Family than about the individual person of the current monarch.
From what I have read, Charles has confirmed that he will use Buckingham Palace as a home and the hub of the Royal Court, in much the same way as the Queen has always done and it sounds as if he wishes to carry on a lot of the time-honoured traditions, so I don’t think much of what tourists come to see will change.
There was a similar situation when Queen Victoria had a very long reign and her son kicked his heels as the Prince of Wales until he was nearly 60.
Victoria had become Queen so young, she never had time to put a foot wrong before she became the monarch and it’s easier for an attractive young Queen to gain popularity with the public - and she gained a reputation for being “morally upright” and synonymous with the “glory of the Empire”.
Her son was left with little to do but enjoy life and anything he did wrong was gossiped about over the years, so by the time he got to throne, he was a bit of an old roué and had a lot of “bad press” to overcome.
Many people doubted his ability to be a decent King, including his own Mother, but when his turn finally came, he turned out to be a successful and popular King and left some good legacies behind after his short 9 year reign.