Yeah I don't like it too. The music is one thing, it's a ear-worm of a soundtrack. But the mod itself it's just not good, there's a lot of flaws from this mod that prevents me from enjoying it.
For one, it's the sprite inconsistency; It looks good don't give me wrong, but it does not fit Terraria at all. It feels like those sprites got ripped from another game, probably a 2D League of Legends game. It's the same issue to Godzilla NES creepypasta as a example, the sprites are so detailed and different than the original game that shattered the believably from the story since day one. Calamity feels like it does not belong to Terraria thanks to that, even if the story/lore told me so.
Second is the balance; the more you play it, the worst it gets. Up to early hardmode is fine (even before you get HM-tier items from Slime God, a pre-hm boss). Afterwards is a cluster

,
it has so much bloat where it easily overshadows the other, and it pays no respect towards vanilla items at all, they're rendered useless by it's own additions, even the
ty calamity item overshadows a vanilla item in hardmode. And to add insult to it's injury, most of the things from 1.4 nerfed to the point it's useless; Zenith is now a post-yharon weapon which means it vastly underperforms, Soaring Insigma now gives you a flight boost instead of infinitely fly around. The stuff that featured in 1.4 where it could be really useful in this mod, now became non-existent because it ruined the mod author's "vision". Btw, Burning Sky is a MELEE weapon when it acts like a MAGE, and it's ironic too considering the older version it looked like a sword:
Now it's this:
View attachment 493007
Now, if you love the mod and it's your favorite, that's fine. I'm not saying you should hate it, there's some good things I like about the mod outside of music, like some of the weapons are based on things I like (Resurrection Butterfly), but for me I don't like the mod as a whole, it's bad. But it's a fun mod on it's own right if I turn off my brain and just enjoy it unconsciously.