To preach the gospel and make disciples.
Nobody said that He didn't need shepherds for His flock.
Jesus gave them their assignments, and gave gifts to the church through the Holy Spirit, but they and we are ambassadors for Christ, not mediators. They have the roles of apostle, preacher, teacher, etc, but not mediator.
That role belongs to Jesus alone. JESUS is the only and only mediator between God and man.
There is no need for any other mediator between God and man nor is there a need for any mediator between Jesus and man.
Again, I intend no sarcasm: have you ever asked someone if they will pray for you, or remember you in their prayers? The Bible says, “pray one for another,” then do to feel that doing so is or is not mediating in some way?
In Acts, when Peter said, “Silver and gold have I none; but what I have, I give to thee: in the Name of Jesus Christ of Nazareth, arise, and walk!” (I love that part!) wasn’t Peter a mediator?