The problem is that the sequel followed the exact same beats as the previous movie. Unfortunately, this highlighted how much better the original Mary Poppins film was. We had a clean up number (Spoonful of Sugar/Can you Imagine That), a performance in an animated world (Supercalifragilisticexpialidocious/A Cover is Not A Book), a visit to one of Mary's cooky relatives (Uncle Albert in the first, cousin Topsy in the sequel), Mary singing a somber lullaby (Feed the Birds/The Place Where Lost Things Go). A chimney sweep dancing sequence is replaced by a lamplighter dancing sequence. Instead of flying a kite, they fly balloons at the end.
It was essentially a remake disguised as a sequel. Sort of like the Force Awakens in Star Wars. And the problem with being so derivative of the original movie is I kept thinking of how much better the first movie's comparative song/sequence was compared to the version we got in the sequel.
Mary Poppins Returns needed more originality. The first movie was bold and inventive for 1964. Mary Poppins Returns felt like an uninspired throwback