'Apophatic' does not mean 'we won't explain it'. It rather means using negative language to precisely locate where the mystery is. This is what the Christological definitions do, for example, in their mix of apophatic and cataphatic language. Transubstantiation does the same thing. It doesn't define the mechanism of the change, but rather by putting forward a type of change for which we have no natural analogy, it eliminates a whole host of erroneous conceptions of change.
But in using the term transubstantiation, you have made a natural analogy. You posit that the body of Christ, whatever it is, has a what-it-is, which replaces and fully consumes the what-it-is of the bread and wine, whatever they are. In an attempt to provide stability for and closure upon our understanding of the mystery of mysteries, you have resorted to appealing to the concept of being. But immediately upon specifying the manner of change as being a change in being, you open a whole can of worms by opening the mystery up to further speculation, which has been validated by the shoving of the mystery into the framework of being. So then what becomes of the remaining accidents? Do they inhere in the what-it-is of the body of Christ? Do they remain without subject? And more importantly how, by eating the remaining accidents, do we become deified? Is it because the body of Christ has become locally present where the accidents are to be found? How is an essence made locally present without manifesting its own form and energies, such as the form and energies of flesh and blood? What is the nature of the body of Christ? Is it His hypostasis? His two natures?
But perhaps you would object by saying that transubstantiation is not meant to subject the mystery to the framework of being. But in that case, you would again make it an empty utterance, since such a denial would mean that the term does not specify the manner of change. And if you try to take refuge in the term homoousion, I would ask, what was meant by the term homoousion? That the Father and the Son, and the relationship between them can be grasped by claiming that they are the same kind of beings which we see around us, which have an essence and an hypostasis? Of course, I would suspect you would rightfully reject such impiety.
So perhaps then you would try to take refuge in saying that the term homoousion similarly makes no claim as to how the Father and Son are one, only stating the fact, and that therefore the use of meaningless words like transubstantiation is justified. But this does not hold, because if one restates the term homoousion in terms of what the word is intended to exclude (that is, homoousion excludes the possibility of that the Son is heteroousion and also certain implications homoiousion) one will see that it is not meant to define the manner of unity, but only that it affirms the fact that Father, Son, and Holy Spirit are one God. By contrast, when we examine only one term alone which transubstantiation is designed to exclude, consubstantiation, it immediately becomes clear that the term indeed aims to define the manner of the change, by excluding the possibility that the essence of the bread remains.
Do you see then? The term itself carries an inherent meaning which encroaches upon explaining the unexplainable by way of privation. Hence we must either qualify that it does not explain how the Eucharistic change happens (which robs the term transubstantiation of its meaning and makes the term nonsensical), or we must admit that we use the term to pry into that which cannot be explained. We are simply better off not using it.