Adam Tornhill has a very useful tool called CodeScene. The tool can do deep analysis of a "git" repo to identify where most changes are occurring and who is doing them. It also identifies which "committers" are responsible for key parts of the code and the potential damage that would occur if those critical "committers" were lost to the organization. The analysis tool can also spot areas of the code that are getting frequent changes that may indicate a problem with design. It's the committers of important features that flags the potentially irreplaceable members of the team.
That is OK but all changes are not equal.
In our work team we had folks who had only one helpful idea every six months—but often it was so creative and powerful that it meant more than the dozens of little improvements other team members generated during the same period.
The problem with truly complex processes is that nobody fully understands them—managers who think they do are often a part of the problem and not part of the solution.