I don't think fetish is used in the psychology sense of the word
fet⋅ish /ˈfɛtɪʃ, ˈfitɪʃ/ Show Spelled Pronunciation [fet-ish, fee-tish] Show IPA
1. an object regarded with awe as being the embodiment or habitation of a potent spirit or as having magical potency.
2. any object, idea, etc., eliciting unquestioning reverence, respect, or devotion: to make a fetish of high grades.
3. Psychology. any object or nongenital part of the body that causes a habitual erotic response or fixation.
So many things are regarded as a ’fetish’ nowadays. It would appear that anyone who claims to have a sexual attraction to such an unappealing object is either lying or has had their mental faculties upset by some severe trauma sic drugs but even if having a highly obsessive attraction to something like diapers is appealing to them, it is probably masking a more unconscious desire, perhaps pedophilia in the case of diapers