It’s an important question, but not a simple one. I hope we would all agree that preaching has much more to do with gift than degree. But which gift? Obviously the gift of teaching is the typical one people point out, or perhaps a carefully defined (or re-defined) gift of prophecy. But what about the gift of evangelist, or a leadership gift, or exhortational / encouragement gifts? It seems that many of the gifts can help in pulpit ministry. Nevertheless, not everyone is able to, nor should, preach.
Those that have that something – divine gifting, calling, unction, whatever – they should then be responsible stewards of what they have been given. That is where the training comes in. The degree or qualification may not matter, but the training does. However we get it, we should look to fan into flame whatever gifting we have by a combination of both experience and training. Certification may not be a big deal, but true education is, however we get it.
Incidentally, perhaps one of the benefits of formal preaching training is that it helps some people learn that they should not be preaching! What church listeners may be too polite to point out, feedback sheets, wise instructors and video recordings can make clear.
So let us be sure that we never rely on gifting without being responsible stewards of all that God has given us for ministry (this means reading, getting training, being a learner, looking for mentors, etc.) Equally, let us never rely on education or academic qualification (this means being fervent in prayer, humble in attitude, reliant on God, etc.) We preach as stewards. It is His ministry.