"The silken tones that Meghan employed on the legal series 'Suits' and which were often muzzled during her time as a full-time royal are now given free rein," Potton wrote on Tuesday.
"And yes, she certainly has an actor's way with a phrase and a likeable sense of mischief. "Oh! Who did that?" she coos in mock disgust when one of the elephant calves breaks wind.
"The sense of performance, though, often feels overegged. Even the underwhelming moment in which the elephants rip some bark off a tree is presented like the announcement of the winner for best picture."
The official premiere of the documentary will be on August 3rd, although most major reviewers have already awarded it only three stars.
Meanwhile, Helen Kelly at Express.co.uk called Meghan "the perfect choice".
She wrote: "Meghan approaches the situation with caution and is measured in her narration.
"She is overall, very respectful of the documentary and its subject.
"This isn't a documentary about Meghan, she is simply narrating and she is very aware of that. This is what makes her the perfect choice."
Elephant was directed by Alastair Fothergill, Mark Linfield and Vanessa Berlowitz, who all reportedly worked on director David Attenborough's "Planet Earth."
Meghan reportedly accepted the voiceover gig in return for a donation to Elephants Without Borders, a non-profit organisation in Botswana that aims to protect the species from poaching.
The duchess allegedly landed the role after her husband, Prince Harry, talked up Meghan's interest in narrating a project to Disney's then-CEO Bob Iger at the London premiere of "The Lion King" last July.
In a video obtained by the Daily Mail, Harry is seen approaching Iger about Meghan doing voiceover work.
"You know, she does voiceovers," Harry could be heard saying to Iger, 68, as the prince pointed to his wife.
"Oh really, I did not know that," Iger said.
"She's really interested," said Harry.
"We'd love to try," Iger responded.
It comes as reports have circulated that Meghan Markle and Prince Harry are ready to have another baby, according to a report by Cosmopolitan Magazine.
Meghan gave birth to her first child, Archie Mountbatten-Windsor, in May last year.
The couple recently moved to LA from Canada, where they had been residing after stepping down from senior royal duties.
Speaking to US Weekly a source said: "They'll be trying in earnest pretty soon. They just want to get firmly settled into their new surroundings first and give Archie as much attention as they can."
The actress recently lent her voice to Disney to create a documentary about elephants in Africa, titled Elephant back in August last year. The film release has recently been pushed forward, correlating with the launch of Disney's streaming network, Disney + and early reviews are in for Meghan's vocal performance.
In one review by Empire's Ian Freer, he said: "Markle's delivery is wholesome and over-eager to please. She just about stays the right side of annoying."
And the reviews don't get much better, as Ed Potton from The Times wrote: "Meghan is swapping pomp and circumstance for schmaltz and cheesiness.
"The departing Duchess of Sussex narrates Disney's tale of a herd of elephants crossing the Kalahari Desert from the Okavango delta to the Zambezi River, and boy does she lay it on thick.