Hello! I've been a long time lurker, first time poster but wanted to add my 2 pence to this thread.
There was an interview in 2016 when MM was still in Suits, that I had really enjoyed as a huge fan of the series. []
She comes across really intelligent, confident and ambitious but it's very telling at 15:33, when she says (About her UN engagements in Africa), that she doesn't "just want to show up somewhere and wave her hand", but get very hands on if her name is attached to it. And I think that really is the crux of the matter. I don't doubt that she does very much care about her causes, probably thought the RF would be a great way to make a difference, but the constraints on how she does charitable work was not her style. She probably thought she could influence the RF to modernise, but they're not the UN - they have a very specific role to play, and it's not the kind she wants.
I don't agree with how she and PH went about the announcement, and I did think the Africa interview was in bad taste (Also the bit where she says that there are no tabloids in North America so she wasn't aware of what to expect...I'm pretty sure the Hollywood paparazzi is notorious!). But mostly I think she and PH are just not a compatible/good match, though they may love another very much. She's very ambitious (something she repeats in that Suits interview), intelligent and used to the freedom of making her own decisions and being accountable for them. He's none of those things, and if he weren't in the RF, he'd definitely be punching.
I think the RF have made the right decision, as have MM and PH. However, I think she will thrive in the new situation and he won't - he's never really had to fend for himself. To that end, I think she was selfish in making it a tough decision he made, between family and wife/child. But again, that is part of her personality and probably what attracted him to her. While I hope things work out for them, I think it's more likely that he will get very unhappy at not receiving the same adulation and respect he gets in the UK (as RF/military), and it will be a struggle as he effectively becomes Mrs. Markle. And will then probably come back to what he knows best. I reckon they're both great separately, it was just a difficult combination to reconcile. It will be interesting to see how their new life does turn out for sure! However, I do appreciate that he has put his wife first, as it's not something a lot of men would do, so even if it all fails, I respect him doing that.