I think Harry blames the RF for his mother's death, and therefore what looks like 'throwing his wider family under the bus' to some is actually Harry desperately trying to avenge his mother and not caring about the consequences to the family because, well, why would he? Whether what he believes is true or not is almost irrelevant - they did his mum wrong, to what extent is arguable but her untimely death and the void she left has elevated her to sainthood and Harry, I think, has taken it upon himself to make them accountable.
Harry knows what goes on behind closed palaces doors - we don't. It must be galling to constantly read about your brothers fairytale marriage whilst your own is scrutinised daily, especially if you knew your brothers fairytale marriage was just that, a carefully constructed tale. Add to that, he knows a lot of those stories are fed to the press by the establishment - seriously, who would feel loyalty in those circumstances?
Plus, all the questions surrounding his mother's death - Harry would've seen the same conspiracies we all have, and has seen first hand the firms spin in all matters royal, his head must be fucked with not knowing what to believe. Then, having his dad marry the same woman who was instrumental in his mother's downfall. Then we expect him to be loyal and quiet so not to upset his family? 
I feel for him, I really do - and I think he found his soul mate in Meghan, with her (I was going to say equally, but that's doubtful) dysfunctional family. I don't think Meghan created this, I think she's just given him the strength to say 'fuck this!' and walk away. He's not alone anymore, and I hope for his sake his marriage lasts.
I could be wrong though 'cos all any of us know about these people is what we have been told. These aren't 'normal' people - their every move is constructed to garner a reaction, even recently sharing a pic of Charlottes Mother's Day card to Diana after negative press from the Oprah interview, if harry had done that he would've been slaughtered 🤷🏻♀️ I wouldn't feel any loyalty to them either, they're not a family, they're a business.