If the Palace can spin such a positive story around Camila (who was so hated when Charles married her it was decided to be best if she didn’t use her Princess of Wales title), they definitely can rehabilitate Harry and “sell” the HI/HO “compromise”.
This comparison keeps getting brought up but it's really an apples and oranges sort of thing.
Firstly, I'd say Camila was kind of a blank slate. The public didn't really know anything about her other than that she was Charles' side piece, and seen as the evil older woman compared to the sainted Diana. As the years passed, and the public slowly saw Camila as a decent enough type who did good work for her charities, while the 'Saint Diana' image faded, Camila became accepted, if never really popular.
By contrast, Harry is very well known and over the past 5 years has gone from being one of the most popular royals to one of the most disliked. It's going to be very hard to reverse that now.
Secondly, Camila just got on with things whereas Harry and his wife are constantly blabbing to the press and can't let anything slide.
Thirdly, Camila is the King's wife and Queen of the United Kingdom. She's one of the most senior royals. Whereas Harry is 5th in line and frankly, not needed.