Here's my take on the movie:
Got out of the theater about an hour ago. Overall the movie was EXTREMELY faithful in tone, the sweeping score and with the magical element that comes along with the character of Mary Poppins. Emily Blunt nails the performance and proves to be a worthy successor in the role to Julie Andrews. When the movie opens with Lin-Manuel Miranda singing "Lovely London Sky" and he has a British accent, I admit it was a bit odd to hear at first. I'm just so used to his normal voice that it threw me off, but it didn't take long for me to buy him as Jack, the lamplighter. Miranda is also a part of what I consider the two best musical sequences in the movie - "A Cover is Not the Book" and "Trip a Little Light Fantastic". The Former being a spectacle with Blunt in a classic 2D Animated world and the latter being a 7-minute showstopper in the vein of "Step In Time". It's not as catchy, but I would argue it's actually more of spectacle. The choreography was perfect and the amount of dancers in the sequence really made it feel incredibly grand.
As to the music and some of the complaints of it not being catchy enough... I see where that point of view can come from. This is no Greatest Showman where every song is an ear worm. There's no "Let It Go" or "How Far I'll Go" here. The way I came out of the theater thinking is that the music may not be something you go singing on your way out of the theater, but I did thoroughly ENJOY all of the musical sequences, with quite a few of them being real stand outs. All of the songs were more than enjoyable while watching the movie and I think that's what really matters.
EDIT:
At the same time, I do feel like there is the argument to be made that Mary Poppins Returns does go almost beat for beat the same as Mary Poppins. That's not necessarily a knock against this movie, but just sort of where to set expectations. It's still a really good movie and deserves the praise it receives, but just like how if you've seen A New Hope you've basically seen The Force Awakens, the same can be applied to this movie if you've seen the original Mary Poppins.
To give another Star Wars Comparison, we could look at SOLO. The entire movie, I never bought Alden Ehrenreich as Han... I kept going back to Harrison Ford. In Mary Poppins Returns however, I never once thought about Julie Andrews while watching the film - Emily Blunt completely owned the character and really made you believe that she was her.
