Just to be clear, I’m not saying teachers or rebbeim should never be fired. What I am saying is that there has to be a balance. You certainly don’t fire a good rebbe just because you think you can find a better one, and even if a rebbe is seriously underperforming, you need to work with him to try to get him to improve.
Firing a long term rebbe needs to be done sometimes, but it should be a last resort.