I actually think the sloppiness arises from simple incompetence. Neither of them are qualified to be spokespeople on public political, social or global issues; neither of them knows anything about entrepreneurialism, marketing and PR; neither of them knows anything about media content production.
The only reason that the media breathlessly reports on Harry or Meghan's every gormless pronouncement or incompetent activity is because Harry has an elevated status due to an accident of birth and Meghan has an elevated status because she married Harry. And to be clear, if Kate and William were suddenly stripped of all their advisory infrastructure, I'm sure they'd prove to be almost as incompetent at getting stuff done (not equally incompetent because, let's face it, H&M have a rare and special sort of reverse Midas touch, in that everything they touch turns to shit).
But the difference is, William and Kate clearly understand what Royalty is all about. K&W know there's nothing particularly special about them as individuals; they are fortunate enough to be representing something much greater, something that isn't just a thing in itself but a constant act of dialogue with and permission-seeking from the general public. That's what royalty is really and that's why it is indeed accurate to think of it as a service rather than a status.
Harry clearly never grasped this; I'm sure plenty of people tried to teach him but, as Spare shows, he has the strange arrogance occasionally found in people who are hard of thinking, but refuse to be taught. Poor old Harry is dumb enough to think he's special in himself, and he's infected Meghan with that belief too. Therefore everything they do, no matter how sloppy, ill-researched and ham-fisted in execution, must be perfect.
The problem is that that belief repeatedly fails to survive direct contact with the real world.