The short version is that while Nav Canada did streamline operations, but the broader shift to privatized air navigation services can be seen as a net negative in many other places for a number of structural reasons.

Safety oversight gets complicated. Even a non-profit private entity answers to a board and has cost pressures, and regulators can't maintain the same level of scrutiny they had over a government department. You see this in the UK where the privatized NATS has faced repeated criticism from regulators over performance and staffing levels affecting service quality. The safety culture shifts from a pure public good to something that must be weighed against operational efficiency.

The non-profit model also hides a loss of public accountability because Nav Canada is not directly answerable to taxpayers in the same way a government service is. Decisions about service cuts at remote airports or staffing reductions are made behind closed doors. Communities that lose air traffic services have very little recourse. In a public system those decisions are politically painful so they face more scrutiny.

The cost savings to airlines do not necessarily translate into lower ticket prices either. Airlines generally pocket the savings and passengers still suffer when the system is stretched too thin during a crisis. The pandemic exposed fragility in many privatized systems just a few years ago.

So yes Nav Canada has a decent reputation on the surface. But privatizing air traffic control erodes safety oversight and public accountability. Some things are natural public goods and should be operated as such.