If H and M wanted to control access, and it's completely understandable why they would, they could have followed the example of the Cambridges, but in a stepped down way. In other words, they could have released a brief statement after the birth , giving the location and time of the birth, without prior statements about what they wouldn't be doing. A photo could have been taken at home by Kate maybe or someone trusted by the family, and released a week or two later. A photo of the whole baby, not bits of him, in colour.
The Instagram could have followed the model of the rest of the RF and been kept brief, factual and only relating to events, not personal commentary or quotes from other sources.
M would have been well advised to ask her 'friends' to keep absolutely silent, as William and Kate's are. Keep all the celebrity lovely nonsense to a minimum.
Not preach about the environment whilst doing nothing personally to take action or make sacrifices.
Make no personal comments about the press (The Lion King).
Be very careful not to be seen to be promoting the interests of friends
Take advice and listen to it.
M to be seen to be interested in learning about the culture of this country, perhaps not spell words in Americanised form on their Instagram would have been a start.
M not turning up in jeans to Wimbledon and then expecting to take up a large amount of seats for herself and friends , and be a prima donna about photos.
William and Kate are pretty much a perfect template of how to control their image but keep maximum privacy. They only had to watch and learn, but they don't want to do that, they want to make statements and draw attention to themselves, they want to be special. The only thing that is special is the institution itself. Prince Charles and Camilla also work the system pretty well. We don't know what they do privately or what they think . If Charles makes statements as he has done in the past about architecture or agriculture etc, he is seen to take action himself to correct the wrongs. He doesn't moan about pesticides then be seen promoting them.