If we accept that you can empathize with a fellow human being without them being your favourite person, does publically saying that your family have caused you mental health problems not risk causing them mental health problems?
There is only one logical way to interpret Harry's work in a favourable way, and that is that Charles, Camilla, William and Catherine don't have feelings, and Harry knows this, and realises that it's absolutely fine to talk about their lives and make audiences look at them in a new disparaging or critical way.
But otherwise, for reasons I personally don't understand, the reason must be that he knows he will be causing them pain and stress but doesn't feel sad about that.
For that to happen he must feel his right trump theirs. The likely cause of this attitude would be a grievance; that he's working on a tit for tat basis, and something big is at stake. My interpretation is that the big thing is his and Meghan's image. My insight would tell me he actually thinks that in not giving them their royal duties and HRH, the royals have robbed him of something. He feels grievously wronged and, in his eyes, is sticking up for himself. I suppose that's the reason for the comment about princesses - it actually matters to him that his family are important royals.
For me, bothering about royal status is shallow, so I won't be feeling sorry for Harry. Those reasons above are why I detest what he's doing, not because I don't feel for him as a fellow ' passenger on the way to the grave' as Dickens would have said.
Harry and Meghan have Sunshine Sachs, so we know they feel it's important to control their own publicity and how audiences perceive them, and still, they want to stop William and Catherine and Charles from controlling narrative: Harry knows he's giving them a headache.