You cannot miss this historical classic!
I suspect that most people have seen Mary Poppins the original, which is an amazing classic, in the opinion of this former child and current parent. Although Poppins Returns is a 'derivative work' in many ways -- you can practically map its structure to the original, and there are elements that are imperfect perhaps, there are superlatives about this film that make it a must see in the humble opinion of this writer. Thanks to Rob Marshall and the majority of his exquisite cast, this film is 'practically perfect in every way'.
I will give brief mention to my perceived negatives. The Ms. Streep scene sounds as though she is attempting to reprise her role as Sophie in Sophie's Choice, but the scene is too busy, too confusing and overall given the length of the film and the value of this number detracts from the value of the film. My kids could not wait for it to end, and I felt the same way. It was annoying. On other notes I do agree with the overall darkness of the film. Too often it was so dark, it was difficult to make out what was happening. A kid's film would be better off using color and light more effectively. I was noting that there was more 'evil' noted in this film than the original, but perhaps that is necessary for lessons learned - the children needed to learn (the particular lesson being taught in that sequence). The nature of the cartoon and the way it played, only for a few seconds, was nothing compared to children's movies of today. At one point, the children's father become's angry with them, which was appropriate, but the script had him take it too far, blaming them for his looming predicament -- not their fault and something for which he did not apologize. That was weak and disappointing. Finally, the movie was long, which would not have mattered if not for the above.
As for the positives, consider every detail of the remaining film. Tremendously original (oscar award-winning), creative, and entertaining. it did not surprise me to see that Rob Marshall was at the helm of this work. It was creatively brilliant. Not just the musical numbers, but the casting and direction the creators of this film had the wisdom to collaborate with the available talent from the original film -- Richard Sherman to consult on songwriting, Dick Van Dyke who still has a role at the Bank, and even a crew of the original penguin animation artists. They were concerned about doing things right, and it shows. Though the framework and the spirit may have been derivative -- it was no crime because it was, after all, a long-awaited sequel to a children's classic, the music was a whole new brand of wonderful. The children and their father were dealing two other heartwrenching crises besides the potential loss of their father's job. They really need Mary Poppins this time! As you may have heard, Emily Blunt as you have never seen her, accompanied by an amazing cast, delivers. Enjoy!