Lin-Manuel "may" not have been a great choice for the movie, as his voice and style are very distinct. That said he gave a wonderful performance. It could have worked if they moved the music more away from Hamilton and made it more distinctly Cuban. Unfortunately, the rest of the movie falls down flat.
The plot has a lot of potential but it never really fleshed out. "The song" that you wait for the whole movie to hear is not well written, it's OK, but nothing special.
The obstacles, well they don't make sense either. It tries to make out like the mother is cruel or uncaring, but she is not. She is never given a chance.
The plot seems to want to be Coco, but Cuban, Or Lilo and Stitch but Cuban, or Home, but Cuban.
Unfortunately, it fails to really showcase any real Cuban culture unless you count a few Spanish words here or there. There's no real conflict or problems to overcome. Unfortunately, the entire movie should have been in the style of Pixar Short.
I hope Lin-Manuel can use the movie as a springboard, but he has to move away from the "Hamelton" style of music. Hopefully, this doesn't typecast him, and instead gets his foot in the door for other movies.