The IG has no power to indict? The IG is being used to waste time and divert attention.
Generally speaking, that fact (it is true) is an academic separation of powers. Congress only recently entertained the notion of giving IG subpoena power, which is necessary to reach a person after they leave government. IOW, "quit and you can't be compelled to testify."
As to the power to prosecute, see DOJ OIG Press releases, loaded with guilty pleas, convictions, etc. Technically none prosecuted by OIG.
OIG is an investigating authority, as is the FBI. The FBI lacks the power to indict, too.