Are there theological explanations for why God chose the Church to preach the gospel instead of more effective and efficient alternatives? If the end goal is the preaching of the gospel to every human on the planet, then it would not be hard to come up with very efficient and effective methods to do so. For example, God could send hundreds of millions of angels to preach the gospel around the world, and in a matter of minutes every person would be evangelized. Or God could give dreams and visions to every person simultaneously revealing the truth of the gospel, causing unprecedented large scale conversions all over the globe (by the way, there is anecdotal evidence that this appears to be happening to Muslims to some degree). And likewise, one could creatively think of myriads of other possible ways in which the gospel could've been preached sooner, faster or more effectively. Yet, God chose to use human beings, the Church, to carry out the great commission. Why?
I don't want this question to be opinion-based, so I would prefer answers that draw on reputable sources pertaining to the subject matter, e.g., the works of reputable theologians. Alternatively, if a denomination has an official denominational answer to the question, I would be interested in knowing that too.
Your question could be expanded: why did God choose to make the world at all?
The implication of asking your question is that the ultimate thing God is aiming for is efficiency. This is not the case.
God created the universe for his own glory. He has his ways of doing things which are not our ways of doing things:

As the heavens are higher than the earth, so are my ways higher than your ways and my thoughts than your thoughts. (Isaiah 55:9)

However, I think we do have some clues as to why God chooses to make the gospel known through frail and flawed human beings rather than in a more 'efficient' way.
2 Corinthians 4:7, &quot;But we have this treasure in jars of clay to show that this all-surpassing power is from God and not from us.&quot; If you think of us as the 'jars of clay', then the fact that something supernatural happens (i.e. people are converted) by the preaching of the gospel shows that it is God's power at work.
Similarly in 2 Corinthians 12:9, &quot;But he said to me, ‘My grace is sufficient for you, for my power is made perfect in weakness.’ Therefore I will boast all the more gladly about my weaknesses, so that Christ’s power may rest on me.&quot;
When God's work is accomplished not only despite our weakness but through our weakness, then it shows it can only be his power and not ours.
So I would answer your question, God chooses to make himself known and evangelise the nations through the work of human beings, because it brings more glory to himself in his power being made manifest in weakness.