It’s been a while since SM had a girl group of Aespa’s level so once Aespa got really popular with Next Level they forced a narrative that a new generation begins only when a top tier group emerges. The issue is that it has become subjective and everyone wants their group to “open the generation”, from BM to ZB1 to H2H. Effectively making the original concept of generations, which is based on years, to one about which fits a particular fandom’s narrative
OP