Simplicity' is a slippery concept, but the best technologies can be learned by looking at the input device and not by studying a manual. Running the program is a different matter. Good technology, by contrast, is intuitive. To use an elevator, I press the floor number. To make a phone call, I dial the number.
Simplicity goes hand in hand with range of function.
The problem with MS-Word and a host of other programs is that they try to be all things for all people. Compare that with GuruNet, which lets me look up any word on my computer screen by alt-clicking over the word. Good technology doesn't require parts. You don't need to replace anything in your telephone. It is easy to overlook parts because they don't seem very much like parts.