I don't think Kaori is being neglected. I think she's being relegated in to that Anisong niche hell where there's little chance to grow a wider fan base. ( I think that's why Asuka / Aira left Spacecraft. She wanted to break out of the niche she was being relegated to.) He last album having an overbearing "game" music theme didn't really help to break her out in to the main stream. I don't know... maybe she can do a collab with a main stream artist to get some attention. She could also do more lives, maybe even a tour (maybe as an opening act). A few concerts a year doesn't help on the promotion side. Kalafina is getting the recognition because they are incessantly touring (with or with out new material).
As for YK, I think her desire to perform live is waning. She's getting older. Her soundtracks keep her very busy. Writing material for Kalafina adds to the pile. FJ's Elemental had only 3 new songs. It's basically a new single lumped in with all the previous released songs (and a See Saw cover) to make an album. (I actually like the album, and I think it influenced the sound of Far on the Water).
Also, writing songs for tv and movie is a lot harder than just jotting down what ever you feel. YK had to re-write To the Beginning because it wasn't what the producers wanted. It's probably not the only time she's had to re-write songs to get producers' approval. (No doubt the rejected songs end up on Kalafina albums or b sides.)