There's two very big differences though.
Firstly, Clarkson (and I'm talking about him purely as a TV presenter now, not his politics or his personality) has a down to earth rough and ready charisma and, crucially, is not afraid to make himself a figure of fun. Indeed I'd say a good 15% of Clarkson's Farm is Clarkson and the other characters inviting the audience to laugh at how fat Clarkson is, how unhealthy he is, how unreconstructed his worldview, and his woeful ignorance about farming.
It takes a special kind of charisma and ease with oneself to be able to invite the audience to laugh at you. I think Meghan would rather spend a year with Harry's old huntin shootin and fishin chums in a stone cottage in the Highlands than permit anyone to laugh at her. Or even give a wry smile.
Secondly, Clarkson had the confidence to give significant stretches of screentime over to secondary characters who were, in fact, more popular with the viewers than he. Kaleb and Charlie being the obvious two. Both fully realised human beings simply being themselves. By contrast, Meghan's secondary characters - her MUA, Mindy Kaling - seemed to be following a very close script and in Kaling's case, seemed actively nervous about departing from it. That's why their exchanges feel stilted and artificial; because they are.
I sense that Meghan is very, very uncomfortable with the prospect or actuality of anyone going 'off script' in her vicinity.