It’s an ambiguous question. Let’s see if I can give the two ways I’m hearing it.
It’s important that every sermon from a Christian preacher be a Christian sermon, that is, a sermon that, if a Jewish or Muslim person heard it, they wouldn’t like. If they like it, something is wrong with it, because they reject Christ as Messiah and crucified and risen as the forgiver of the sins of the world.
And since they reject it, if they hear a sermon that they’re totally OK with, then something is missing. The sermon should somehow communicate that this is all based on and aiming toward the work of Christ and the glory of Christ.
Read the rest here How important is it for preachers to preach Christ from every text of Scripture?.