Well, it is true... But even the closed systems could and probably will offer more and more possibilities for adding good quality sounds.
On the other hand, let's be honest, it is much that can be done with the sounds on-board and yet we all the time want/need more. I guess it's just the human nature. If we understand what an arranger is for and what a VSTi collection is for, we'll have more of a "peace of mind".