Feist might think that it’s become unnecessarily complicated and abandoned it in favour of iZotope’s Spire, but a lot of artists still use GarageBand for demoing new material. In fact, plenty of music has been taken to completion in Apple’s software - Steve Lacy’s Demo, for example, his 2017 debut EP.
In a video for Wired that was released that same year, a then 18-year-old Lacy explains how he makes all of his music using GarageBand on his iPhone. He starts with a drum loop and then plugs his guitar into the phone via an IK Multimedia iRig interface and starts recording.