"Disruption" is an overused term, not an overused idea. True disruption, following Christensen's model, must involve a higher barrier for incumbents than just sprouting a new product line. If their expertise, infrastructure, and/or market position allows them to do that, they will . . . and they will probably win. Even most of Christensen's own examples fail to work the way true disruption must.

True disruption does occur, when a fundamentally different and fundamentally better way of doing something comes along, but it's a lot rarer than people suppose or pretend. It's barely more common than creating a whole new industry. 99% of the time when people talk about disruption they really mean nothing more than basic product/service differentiation.