The indenter is working with QtQuick import without much issue.
But as soon as you use your own component, or import QtQuick as QML for example, it doesn't work anymore.

You'll find attached an example file, with the indentation I expect (maybe one more tab after the delegate: and model:, but it's no big deal).
Open the file in Qt Creator, select all and then call auto-indent (Ctrl+I): the file is un-readable.