I actually quite liked it. Admittedly, it didn't add much to the story, but if SE added something with high significance to the story then so many fans would be complaining saying "Why add that? The story was fine how it is!" But the addittion Souls of Rebirth just made the game longer and allowed us to play with the cool characters again (Mindu/Minwu is my favorite), and who's gonna complain about that?

I much prefered the added story in II than FFI's bonus dungeons, they were just long, annoying and the items you get aren't great. I mean, the reward items weren't bad, it's just that for the amount of time and effort (which wasn't that much) they weren't worth it.