I think automation has lead to complacency, but I also think that the ease with which we navigate today, the advanced displays, the nav systems and GPS, and it's presentation tends to make many lazy. When one has scarcely but to press a button to see the minues of fuel remaining, time to an alternate, landing weight, and any other parameter of a given flight, the mental process numbs and becomes weak.
Automation itself doesn't cause complacency, any more than advanced nav equipment reduces one's skills or thoughts process. Rather, it's the giving one's self over to the automation and the advanced displays, equipment, and capabilities, and allowing one' self to become complacent that leads to the demise.
In the end, the ability to operate with the sophistication that many aircraft and operations do today doesn't of it's own accord make one complacent, but it does open the door and make it a lot easier to get that way.