I also agree with you, but I think there are good reasons teachers face this more than other people. Everybody has been educated, all we have been exposed to the work of educators. All we have thousands of hours of experience of how the education system works. That does not make us capable of doing their work (and, certainly, it does not make us capable of doing their work better), but everybody has a relatively well formed opinion. On the other hand, most people do not have an opinion about how to improve programming languages, for example.