Wicked: For Good is "not quite Wicked: For Great", said Empire's John Nugent in a three-star review.
Total Film's Molly Edwards praised the film as an "absolute triumph", but added it "suffers slightly from thinner source material and weak new songs".
The Wizard of Oz spin-off, adapted from the hugely successful stage musical, is originally based on a 1995 book by Gregory Maguire.
The second film provides fresh origin stories for Dorothy's travel companions in Oz - the Cowardly Lion, Scarecrow and Tin Man.
Wicked: For Good also sees Jeff Goldblum return as the Wizard, alongside Michelle Yeoh as Madame Morrible and Jonathan Bailey as Fiyero.
The i paper's Francesca Steele said: "It doesn't quite reach the heights of Part One, but this is still a highly entertaining display of what musical theatre can do on screen with top level performances and a true affection for the world-building."
Many critics were less enthusiastic. "There's no magic in this aimless slog of a sequel," said the Independent's Clarisse Loughrey in a two-star review.
"If your complaint about last year's Wicked was that it was so oddly lit that you could barely see what was going on, then fear not – in Wicked: For Good, you won't mind so much, because there's so little to look at."
In a one-star review, the Telegraph's Robbie Collin said: "It doesn't amount to two hours of story – the stage show clips through the same plot in around half the time – and the padding is as obvious as it is exhausting."
He suggested the central pair's friendship "rings false", adding: "What should be piercing, impassioned moments are by turns frivolous and sappy."
However, Kevin Maher of the Times was much more positive, awarding the film four stars.
"They've only gone and done it," he said. "The makers of this musical sequel have delivered a film that surpasses last year's box-office smash in verve, ambition and emotional ache."
Both movies have been directed by Jon M Chu, who was also behind Crazy Rich Asians, In The Heights and Now You See Me 2.
Chu is also set to direct a new big-screen adaptation of Joseph and the Amazing Technicolor Dreamcoat, pencilled in for release in 2027.
Many critics highlighted Grande's performance in Wicked: For Good, with several predicting another supporting actress nomination at the Oscars in March.
Variety's Peter Debruge said the pop star shows "fragility" in her more "nuanced" performance.
"Whereas Grande had a relatively one-dimensional role to play in part one, Glinda now faces a complex evolution," he said.
"Grande has been acting since she was a kid," noted the Hollywood Reporter's David Rooney, "and her quiet moments of introspection, anxiety or sadness show tender depths, as does her loyalty to Elphaba."
But he also praised her co-star. "Make no mistake, Erivo remains a powerhouse, with pipes that shake the heavens and a wellspring of unforced emotional intensity that never runs dry."
"What a performance from Erivo," agreed the Guardian's Peter Bradshaw in a four-star review.
He added the sequel as a whole "keeps the rainbow-coloured dreaminess and the Broadway show tune zinginess from part one".
The stage musical was split into two parts for its film adaptation, but the two movies were filmed in one go.
The first was released last November and grossed more than £750m at the box office worldwide.
It went on to win two Oscars and two Baftas, for costume and production design, as well as the cinematic and box office achievement prize at the Golden Globes.
One problem facing the sequel is that most of Wicked's best-known songs, including Popular and The Wizard and I, appeared in the first film.
It's an issue it shares with the Broadway and West End musical. "On stage, the second act lacks a song as strong as Defying Gravity," Debruge noted.
In his Empire review of Wicked: For Good, Nugent concluded: "The tone is different from that of the first film: less peppy, more glum.
"With the exception of Goldblum - who appears to be acting in his own film, delighting in stuttery drollness - all the characters are much less cheerful than they were last time around, and as a result it's less enjoyable for us to watch."