I like this point.
The chain of events that have begun to reshape our protagonist, and the tendrils that connect things back to him.
I do think things in the long run may end up being more connected than they currently are (with the possibility that the mc's mom knew Jill's family or something like that, however that may have been "subliminally" pummeled into my skull by the conspiracy theorists here to the point that I'm believing nonsense...)
Jill does fill the role of the hot (not "HOT" in this case) untouchable girl in all the high school/college comedies and she's the only reason he's running foul of Tybalt, one of the games significant (even if buffoonish) antagonists. Take Jill out, and the entire arc with the preps disappears. Tybalt doesn't even care that the DIKs sabotaged his party, he's only focused on the mc, because of Jill.
Also Jill further compounds the mc's love of music. Apart from teaching Sage, there is no one else in the game that he can discuss music with on a level beyond what songs they like.
Although Bella is part of Jill's arc, and there could be a lot of tension (between the two girls and the mc) to come, currently Bella's drama exists in her own unknown world, and if she was taken from the game the biggest ripple would be the upset from her fans.
I think the music probably makes the game stand out more than any other feature but it's hard to assess.
When I hear a song from this game (KFC are using one of the songs from the bar scene with Nicole right now), it so "brings back memories". So is it the music that makes the game, or the game that makes the music.
I probably wouldn't give a shit about the music if I didn't associate it with the game, but I think I'd enjoy the game significantly less if it wasn't for the well chosen music.