Imagine you are CEO and you need to debut new girl group

5-6 members is the ideal, 7 is already pushing it... no kpop group should have more than 8 or 9 members, is just not efficient at all unless you plan to use big number of dancers doing ultra synchronized choreos to create some sort of visual impact like loona and seventeen did sometimes. 4 or below is too risky, you need some insane talented cherry picked idols for it to work out well, and most 4 member girl groups don't get it right.