And then some newcomer comes in and disrupts Uber, and the cycle repeats. Except, this time, there's an opportunity for there to be change, and riders will briefly have gotten a better experience than before.

It's not necessarily a bad thing for business models to be cyclical. Even when it results in a downwards spiral, it usually allows the problem space to be explored, and that spiral can be disrupted upwards... at the cost of temporary lack of quality.