Like Sign said. She is on hiatus. Even if they tried to "apologize" she wouldn't come back. They aren't going to apologize to her anyways. It was her father that convinced Utada to leave, so he would be the one they need to talk to. Also, she would only demand a higher compensation rate that probably doesn't match the work she is putting out.
And we can't keep reusing these songs. They do get tiring to hear and less relevant to the plot. We need something fresh. S&C worked for BBS because that was how they worked the opening out. It is easy enough to work your video to match a song's lyrics.
If SE and Disney have to hire a new artist, so be it. They have hundreds of people to call upon for songs. One singer who is on hiatus isn't worth their time.