Season six of the royal drama depicts the events of the late 1990s, including Princess Diana's death.
It also covers the aftermath of her death in which 'ghost Diana' appears to Prince Charles and the Queen.
In a one-star review, the Guardian saidthe "Diana-obsessed series is the very definition of bad writing".
"Beyond all its formal failures, late-period Crown is also impossibly hamstrung by being set well within living memory. Even if there were anything to engage with, the memories and consequent questions that crowd into the viewer's mind at every stage would make it impossible," wrote Lucy Mangan.
"It started teetering in season three, lost its balance entirely over the next two and is now plummeting into the abyss."
She added that this was "despite the uniformly brilliant performances from the entire cast".
Anita Singh of The Telegraph echoed the Guardian, writing that the "Netflix jewel hits a dead end" as the new season is "haunted by Princess Diana's bizarre ghost".
Her two-star reviewnotes that the use of Diana's ghost "on the plane home from Paris to comfort a distraught Prince of Wales, and on the sofa at Balmoral to give the Queen some friendly PR advice", ends up sounding "like desperation on the part of writer Peter Morgan" who created the hugely popular show which has been running since 2016.
Singh also criticised the handling of the the car crash scene, writing: "The chaos of Diana and Dodi's final day in Paris is conveyed but there are no scenes inside the Pont d'Alma tunnel: we cut from the sound of the crash to the phone ringing at Balmoral. All dialogue in which someone breaks the news of Diana's death has been dubbed out; their mouths move in silence, and we focus on the reactions.
"Why do this? If it's for reasons of taste, why have the camera capture the bewildered face of Harry as he mouths the word "no"? Good taste would mean leaving this scene to our imagination."
BBC Culture's two star reviewdescribed the final season is a "clumsy, predictable end to the royal family drama" and while it has been a "joy to watch over the years, too often in these predictable last seasons... we could have written the story ourselves."
Despite afour-star review from The Times, Carol Midgley noted that Diana's ghost "wasn't the show's finest hour" and was "peculiarly self-defeating in an otherwise powerful and moving opening four-episode suite".
However, the review goes on to praise Elizabeth Debicki's performance as Diana, calling it "outstanding".
"The empathy with which she portrays the last eight weeks of Diana's life and the likeness to Diana is extraordinary, that flirty cocking of the head, a slightly lost, lonely soul who ends up in various swimsuits in the gaudy Hello! mag environs of Mohamed Al Fayed's yacht."
Variety's Aramide Tinubualso picks up on Diana and Dodi's relationship, writing: "Morgan doesn't offer a whirlwind romance but a depiction of a comforting friendship that had only started to blossom and was exacerbated by public perception and familial obligation."
He adds that the new season has helped the show "reclaim its glittering throne".
Empire's four-star reviewalso praises the new season, saying: "This is the most emotional The Crown has ever been, using a mix of tears, real-life footage and 'ghosts' to grieve for the Princess all over again. However you feel about these ghosts - which include Dodi as well as Diana - episode four remains an unforgettable hour that elevates the season as a whole."
The new season covers the media frenzy around Diana and Dodi's (Khalid Abdalla) relationship, culminating in the paparazzi chase that caused the car they were both in to crash in a tunnel in Paris. Both died on 31 August 1997 along with the car's driver Henri Paul, who was found, along with the paparazzi, to be "grossly negligent" at the inquest.
The series also portrays the immediate events following the fatal car accident, including reactions and responses from the Queen and Al Fayed and Prince William trying to integrate back into life at Eton following his mother's death.
Speaking at the Edinburgh TV Festival earlier this year,producers said the subject of Diana's death has been treated "sensitively".
However,Time Magazine's Judy Berman wrotethat the new season is "weirdly audacious" as it is  "milking the mystery of Diana's last days - as well as, unfortunately, her imagined afterlife - for manufactured poignancy. Like the tragedy on which it fixates, it's a wreck on a scale that the show has never seen before."
TheFinancial Times's three-star reviewdescribed those scenes as "indicative of a series lacking inspiration; all too happy to take emotive shortcuts which externalise the complexity of the royals' shock and grief".
The show has also been met with criticism over historical inaccuracies.
Kelly Swaby, a royal historian, told the BBC: "As a historian it sometimes makes me want to cry.
"Viewers often expect a certain degree of accuracy with the show because the production quality is so high, but we don't always get that."
Ms Swaby said The Crown will have taken "artistic licence" on how sensitive events are depicted, not least because "no-one knows what happened in private events" such as how Prince Charles broke the news of Diana's death to his sons.
Netflix previously said the show "has always been presented as a drama based on historical events".
A two-star review from the Independentnotes the show "routinely privileges gossip over emotional resonance: highly speculative conversations between Diana and Dodi are included - and drive the plot".
Nick Hilton adds that the "tabloid tone relegates Staunton's Queen to a side character, while Lesley Manville's Princess Margaret slips by entirely unnoticed."
The Hollywood Reporter's Daniel Feinbergalso criticises the portrayal of other characters, writing that the third episode specifically "becomes a rather brutal hatchet job on Dodi, presented as a spineless man-child, and father Mohamed Al-Fayed (Salim Daw), who becomes a scheming Machiavellian stereotype that has no resemblance to the sympathetic and nuanced version of the character we met in season five."
The remaining six episodes of the new season will be released on 14 December.
The second half of the final season, released in December, will cover events including the Queen's Golden Jubilee, Prince Charles and Camilla's wedding and the courtship of William and Kate - now the Prince and Princess of Wales - at the University of St Andrews.
Princes William and Harry will be played by Ed McVey and Luther Ford respectively in the second half of the season. Kate Middleton will be played by Meg Bellamy.
It is the first major role for all three of the young actors.
The first four episodes of the final series of Netflix's The Crown have split critics, but many have given it the thumbs down.