Clearly there are examples where private ownership is not an effective solution.

The energy industry for example. There is no incentive to promote clean, free sources of energy, such as Tesla's Wardenclyffe Tower. This tower was designed to provide free energy for the entire planet, but was shut down by George Westinghouse when he realized there would be no enduring profit to be made.

The economic incentive principle works in some cases, but in others it works to the detriment of humanity and the ecosystem as a whole.