It is much more complex than that.
I think that paraphilias have some of the features of illnesses, as does depression, OCD, anxiety, and so on. However, I also think that there are aspects to all of these problems which are (or can be), to a greater or lesser extent, under the control of the person experiencing them.
So there are (at least) two factors at play: the severity of the psychological state, and the ability of the person experiencing it to manage it.
The problem with labelling things - especially psychological things - as "illnesses" is that the label connotes the idea that they are in some way beyond the control of the sufferer to manage. On the other hand, I think it is unreasonable to characterise them as lifestyle choices or elective behaviours, because frequently the people exhibiting them, even if they might potentially be able to manage them, lack the skills to do so, and need to acquire those before they can be said to have any degree of control over them.