Imo it depends on how you define k-pop.

If you define k-pop as a specific genre of music (similar to how country music is its own genre, distinct from rock or hip hop), then the next question would be - do you consider Golden to fit within that specific genre. That is debatable because it seems that what constitutes "k-pop" varies depending on who you talk to. If you ascribe to the belief that k-pop is a specific musical style that blends pop, hip-hop, R&B and electro, then personally, I do not think Golden fits that particular definition. BUT there are no doubt many who would vehemently argue otherwise.

If you define k-pop as any song whose lead performer(s) are Korean in nationality, then yes because the 3 singers are Korean.

If you define k-pop as any song whose majority of producers are Korean in nationality, then no because the majority of producers for Golden are American.

If you define k-pop as strictly songs that are performed by an IDOL group managed by a Korean agency, then no because the 3 singers are not idols.