I like how ZUN is dabbling into other music in DDC rather than just 'Jazz/Rock fusion with a hint of loli' like he usually does. I like diversity a lot, and this game has a lot of it, which really suits the diversity of the characters.
Strangely, the themes remind of things they shouldn't remind me of. Like, Wakasagihime's theme makes me think of Dolphin Rider Koishi, the Tsukumo's theme makes me think of London, and Sukuna's makes me think of 'Mirror, Mirror' from RWBY. There's a verse in the song that sounds like a verse from Mirror Mirror.
Also, ZUN made a total call back to Retribution for the Eternal Night in Bamboo Forest of the Full Moon.