I think their root problem seems to be rushing (plus of course the fact that they left just at the start of a pandemic which affected momentum and planning.) Even before the marriage they don't seem to have sat down and really thought about their place in the family and what they could focus on, hitting the ground running is very vague. They had plenty of time ahead of them but it always feels to me like they don't think that way.
I watched a documentary about a Princess Anne at 70 and she was speaking about her work with Save the Children. She started at 21 and said she spent the first five years learning about the work of the charity before she even made a speech. She also said that she couldn't change anything but she could draw attention to the people who were changing things.
I think that if Harry and Meghan had taken time to talk with some advisors they trusted about their plans and difficulties they may have left in a way that launched them more successfully. I would have loved to see them spend some years thinking and learning about their different areas of interests and the variety of charities involved in each area. They could have done a kind of internship at each one they were attracted to, seeing things from grassroots and up and then thought about how they could bring their public profile to best to amplify the work the charity was doing.
They could have done great work either in or out of the Royal family if they had focused. I don't think it is too late for them, they just need to stop speaking about the royals publicly, and turn their focus to be more outward and positive. Harry already has Invictus which is a great arena for him to campaign and bring awareness.
Maybe too a little downsizing would help, even with the money they have their life style seems in excess of their income.
I hope they do take a step back to move beyond the past, find some peace and focus how they want to go from here. I think that Meghan is possibly further along that path than Harry