"To identify Britain’s 100 Most Popular Tourist Attractions, CEOWORLD magazine reviewed data from the Association of Leading Visitor Attractions (ALVA), one of the UK’s leading tourism organisations."

In their list of 100 (I had to choose a year before the pandemic influenced numbers, which in this case was 2017), the only one with a direct connection to the current royals was Kensington Palace at no 57. You could, I suppose, claim connections for the Tower of London, Hampton Court, etc., though those historical sites would still be attracting tourists had the royals been abolished 200 years ago!

There are other lists, of course, but this at least gives the flavour...