The sad thing is, that in isolation, the episode was done very well and was enjoyable. Christina Chong has a hell of a set of pipes!
The problem for me is that it was tonally off from the rest of Star Trek. It was a bold experiment, but for me it didn't fully land. Overall though, as I said, in isolation it's enjoyable and has some good tunes. Musicals aren't everyone's taste, so I can fully understand some people hating it. However, it's a single episode of an otherwise exceptionally entertaining show, so I am willing to forgive. And after all, it's not like this single episode has replaced all the other episodes of Star Trek.
The Lower Decks crossover episode made up for this...