This movie was very much made over the dead body of the creator of Mary Poppins, author P. L. Travers. P.L. Travers and the story of creating the original film was brought to screen in Saving Mr. Banks. Much of Saving Mr. Banks is fictitious. The estate of P. L. Travers green-lit both Mary Poppins Returns and Saving Mr. Banks. P. L. Travers actively denied Disney's repeated request to make a sequel to Mary Poppins. The Hollywood reporter has a good explanation of the what it took to get this movie to screens: https://www.hollywoodreporter.com/features/mary-poppins-returns-how-rob-marshall-brought-it-big-screen-1166094 I start my review with everything above because I feel it is important to have a background on this film. It also helps explain why it took so long for Disney's largest live action hit of the 1960s to get a sequel.
This is an average movie. It was directed by Rob Marshall, who also directed Chicago. Lin-Manuel Miranda is the male sidekick to Mary Poppins. He had no involvement in writing any of the songs in the movie, so don't expect Hamilton. Emily Blunt is Mary Poppins and does a fine job of being stern with hints of sly cheerfulness.
The story is about the Banks family saving their house and the children doing what they can to help. Mary Poppins doesn't actually help the family save the house when you step back and think about it. She keeps the kids distracted while the parents fail at saving the house. In the end one magical move gives the Banks family the few extra minutes they need. The lamp lighters actually provide more help to the Banks family than Mary Poppins.
The songs in the original movie are such a memorable part. The sign of a good sing-a-long movie is that you can start singing along before the song ends. Only two songs in the entire musical met this criteria. So many songs weren't catchy or simple enough to pick up on the first listening.
There are only two animated portions of this movie, neither were as whimsical as any of the original Mary Poppins animated scenes. Adding more animation and making it more fun would certainly have helped Mary Poppins Returns.
My favorite part of the movie is when the lamp lighters get RAD. They use bicycles to get from lamp to lamp. Some of them can do some pretty sweet BMX tricks. I liked that more than a dance number on soot covered London rooftops.
I don't think this movie will ever be considered a classic like the original. There are a lot of politics surrounding the movie that also make it controversial. The cast was fine, but the music was mediocre despite having two capable singers. I doubt kids will be clamoring to have repeated viewings of this movie. A one time rental is probably a safe bet over buying the movie.