It depends on the change being made and why the change was made.
Sometimes a person, such as Elon Musk, can be so associated with the success or vision of a company that to swap them out for another CEO can have a profound impact on the way a company is perceived by the market. Good leadership is as asset to a company, while poor leadership is a liability. The ultimate judge of whether a leadership change is a positive or negative for a company is the market. A change for the better is likely to result in an increase in the company's share price, while a change for the worse may result in a share price decline. If there is no reaction by the market then you can probably safely assume that the change is neither positive or negative, or is at least perceived this way by market participants.
If a number of executives walk away from a company at the same time or in quick succession, it might be a sign a company is in trouble. In a case like this you should definitely do your own research into why this occurred and make an informed decision about whether or not to stay invested in the company.