Personally, I don't like musicals in general because in many of them, the song'n'dance feels out-of-place and breaks immersion. Hence, why I don't like Mama Mia or Westside Story. In movies that integrate the singing and dancing into the actual plot, such as Chicago (where the song and dance shows us that Roxy is going crazy and is used to demonstrate her perceptions, in stark contrast to what we see ordinarily) or The Phantom of the Opera (wherein the music is an analogue, if not an instrument, for magic and beguiling charm), or even The Music Man (in which the music plays a role akin to a montage, and we see other people reacting to the music as they would to the implied activity) then I might be more interested.
And then there's The Producers, where you simply aren't supposed to take the plot seriously, so there's little immersion of that sort for the song'n'dance to break.
...I did a terrible job of explaining how I hate musicals, listing four I love.