Here’s another idea that we too easily believe:
6. A sermon is just the sum of its parts.
That is to say, a sermon consists of explanation combined with application and some illustrations. There is an element of truth here, but it would be naïve to think that it is that simple.
A. There are basic components of a biblical sermon. Essentially there are sermon components like the introduction and the conclusion. And there are ingredients that go into the body of a sermon, such as explanation, application and so-called illustration. At a certain level every sermon could be analysed and found to include these components and ingredients.
B. There are nuances that influence the effectiveness of each of those components and ingredients. For example, there is no such thing as a good illustration, there is such a thing as a good illustration of something. A good explanation for one group of people will fly completely over the heads of another crowd.
C. There are less tangible influences on the effectiveness of a sermon. We could go in many directions here, but lets think about the preacher. What influences how the preacher preaches the components and ingredients of a sermon? The preacher’s love for God and love for the listener is hard to quantify, but it surely influences the choice of sermon ingredients and their delivery. The preacher’s personal baggage is a filter through which every sermon is processed and preached. If a preacher is struggling with pride, then in some way it will show in the sermon. If a preacher is angry, then in some way it will show in the sermon.
A sermon is not just the ingredients of explanation, application and illustrations blended together with sermon components like an introduction and a conclusion. The effectiveness of a sermon goes much deeper than the quality of the elements that are blended together. There is also the moving dynamic of those listening, the occasion, as well as the preacher’s ability, style of communication and so much more. There are complex nuances influencing every aspect of a sermon. Let’s prayerfully keep learning so that we can be the best stewards of the preaching privilege that we can.
Biblical Preaching 
Actually, I’d argue that even here you skip over one of the most important aspects of a sermon, and the most easily omitted: the narrative. A good sermon has to tell a story — to start from one point and pass through a sequence of related points in sequence to arrive at a destination. What I hear too often is a sermon consisting entirely of good points, but where those points don’t really bear any relation to each other — for example, you could switch around the order of the points without doing any damage. The sad truth is that however good the individual points made in such a sermon, they tend to slip away from listeners’ minds unless they’re part of a narrative.
You rightly say “there are ingredients that go into the body of a sermon, such as explanation, application and so-called illustration. At a certain level every sermon could be analysed and found to include these components and ingredients” — and of course we could also rightly say that at a certain level The Lion, the Witch and the Wardrobe can be analysed and found to consist of words printed on paper. It’s not just about what what words are used or even how they are composed into sentences, paragraphs and scenes; but also the order of the scenes that tells a story. That’s (one of the things) we need more of!