I disagree! It might seem like there is nothing to innovate but there is always more! But until we don’t see it, it seems obvious that there is nothing else to add.
Taking the first iPhone in 2007 as an example, the keyboard was replaced by a virtual one, the screen got larger and this started a chain-reaction which gave us new apps, new software and new interactions.
Sometimes a small detail can start a new wave of “ideas” if you want to call it that.