Am I missing something about Sweeney Todd?

I saw Sweeney Todd a few days ago and I just didn't get it. I have gotten into theater recently this past year and have seen about 35 shows on and off Broadway. I lean heavily towards straight plays but have seen a few musicals (Phantom of the Opera, A Strange Loop, KPop, Shucked) and understand that it's more of a spectacle because the staging is usually really complex and impressive in its own right.I suppose similar to challenging films, I usually have to watch an explainer video or read through subreddits to understand the import of a particular film and I can usually appreciate it better after some research. So maybe there is something I'm missing from Sweeney Todd? Some historical significance (when it was written) or musical acrobatics that I'm unaware of? I fully respect the strong performances of Josh Groban, Annaleigh Ashford and Gaten Matarazzo in the show (most notably impressed by Gaten because I didn't know he could sing). I also liked how the chair was used and the choreography of that scene.I guess my problem was I couldn't quite make out the words as people were singing. Was I supposed to do my research before the show? I never watched the movie but knew the gist of the story and was actually surprised by the end. But, was I supposed to like Sweeney Todd or care about his daughter's story? Was the story just a vehicle for people to sing and move together en masse (kind of like when I use a tortilla chip as a vehicle to get the guacamole in my mouth, not necessarily caring too much about the chip but really just wanting the gauc)? I'm really not trying to yuck anyone's yum if Sweeney Todd is your jam but I honestly would like to know why it's great? I am open to having my mind blown and regretting not appreciating it more while I was there.

EDIT:

I really appreciate everyone who was helpful in this thread. I really wanted to know from a more intellectual reason why Sweeney Todd is great and I think I got a lot of good answers. A simple, circular argument of 'Sweeney Todd is great because Sweeney Todd is great' would not have sufficed and I am glad everyone exceeded my expectations with their thoughtful responses. I also learned a lot, especially about this idea of 'dies irae', which was completely foreign to me. It was a bit of a thorn in my side that I didn't understand the import of the show but I have a lot to learn. I realize that I didn't have the vocabulary or experience with musicals to 'get it'. It's like learning about the motif in Beethoveen's 5th and how it plays throughout the movements. I could always recognize Beethoven's 5th and always thought it was meh but learning about how that motif wanders all over the piece makes it that much more interesting. Also to know that someone deliberately and methodically composed this piece so that there was something that would tie it all together and for it to sound great is really impressive. It's also like understanding what was happening in Hong Kong in the 90s to better appreciate a film like In the Mood For Love. There's a lot that goes into the music that I was not aware of.

I want to thank everyone who responded. I really wanted to learn and did not mean to come off as combative or condescending or pretentious. I also want to acknowledge all those who said maybe musicals aren't my cup of tea. I think I'm more comfortable with expressing that about myself but I really wanted to give it a try before swearing off musicals. I mean, if Broadway in NYC doesn't sway my muscials-barometer, I don't think anywhere else I would . I didn't want to be that person that says I'm not into musicals but never having seen a musical. I mean, I never understood Broadway as an entity until this past year and something like American Buffalo changed my mind.