It seems to me that it is apparently mostly forgotten in the “Public Square” that sexuality only exists in the natural world for the propagation of species. This is also true for human beings. If sex did not exist, we would not be here.
Therefore, we say that sexuality is ordered for the continuance of each kind of living thing — including us. Putting it to an unrelated use is therefore a “disordered” utilization.
In some of the “lower orders” of living things, notably the mammals and possibly birds, this seems to have been facilitated by a perception of pleasure for the individual creatures performing the sexual act. Nevertheless, they do not have the capacity to understand this and do not have the free will to engage in it or not.
Of all of the living creatures, only humans have this capacity. We understand that the sexual act provides physical pleasure. We should also understand that when it is open to new life, it also helps bond the two complementary (female and male) partners into a lifelong union that serves them and their children.
When it is not open to new life then, as stated before, it is an act disordered for its natural purpose and it is a deviation from the higher human understanding of its purpose and a yielding to baser, animal instincts.