I don't think you can blame either of them. They both have advisors who are not realising the problems caused by the conflict between what they actually do and how they come across.
The young Royals all did/do well highlighting issues of mental health because everyone recognises no amount of wealth would protect you from those problems.
Harry has been wealthy and famous all his life. Meghan ditto (to a lesser extent) for much of her adult life.
It is quite possible neither of them sees any irony in addressing climate change while needlessly nipping about in aeroplanes; massively oversubscribed baby showers for one child when so many are living in poverty or pointing out the dangers of Instagram etc to people who cannot afford the protections and online security afforded to the well-off.
However, somebody at a lower level should be advising them from a real-life perspective that Do As I Say Not As I Do is OK if you've earned the right to say it or have the hard experience to back it up.
They are not the first to be caught in this conundrum.
Highly-paid TV stars who get kudos for urging us all to "give what we can" could probably afford to donate much more of their own cash to solve the hunger, poverty and need that they highlight for 5 minutes on appeals, while being wined, dined and cossetted in the backstage Green Room, for example.
And most of them should really know better unless they were born into massive inherited wealth.