How do I tell the difference between a business problem and a people problem?
Count.
One person failing in this seat: probably the person.
Two people failing in similar ways: investigate the role.
Three people failing in the same shape: the role is doing it.
Counting tells you which one. Look at the pattern before looking at the person.
Why the count matters
One failure is data. Three failures is a pattern. Patterns belong to systems, not people. If three capable humans cannot succeed in your role, the role is making them fail.