Your view of the importance of delivery in preaching may reveal a deeper theological issue. I don’t want to overstate this, because there are numerous factors involved in a person’s view of the importance of delivery. The general view of those in our “tradition,” the training we’ve received, the perception of what is spiritual, etc. But there does seem to be a correlation between one’s view of sermon delivery and one’s view of God.
If God is essentially a giver of information and requirement, i.e. the distant unknowable deity of classical theism, then delivery will not seem so important. The job of the preacher is to put the information before the people. What they do with that information is between them and God. Some will emphasize that it is only God’s Spirit than can vivify the spoken word in the minds and wills of those hearing. Others may emphasize that the listeners are duty-bound to act on what they hear. However, whatever the theological position, there tends to be a distrust of any focus on delivery since some sort of performance may well muddy the waters of the relatively simple information-only view of Christianity. To touch the heart must be manipulative and somehow not of God, since He is pure mind and will. Thus the preacher should be as plain as possible, so that it is the message alone that touches listeners and glory goes to Christ alone.
Whether they are right or wrong in their understanding, all would agree that the glory must go to Christ alone. However, is there another view?
If God is essentially a giver of Himself, a communicator, a relator, i.e. the made-known God of biblical trinitarian Christianity, then delivery suddenly becomes more important. The job of the preacher is be God’s spokesperson, re-presenting the inspired message of the text, and thereby offering God to the listeners. What they do with that communication is ultimately between them and God, yet it is by no means a “mere information” approach to preaching. It involves heart-to-heart communication, it involves person-to-person connection, it is about relationship even in the course of a “monological” sermon. It is possible to abuse delivery by making it into a fake performance issue (but that is inherently opposed to the authentic relational communication of a God who comes to us genuinely in the Son and by the Spirit). So we should not over-react to “performance” or “sales pitch” trickery by disavowing all attention to communication. Rather we look to be genuine/natural and effective/engaging/compelling communicators. Is God glorified by poor or unthought-through communication? Since God is such an effective communicator, such an engaging communion of three persons, such a captivating lover, surely we must seek to be the best communicators we can be as we represent His Word to others?