Theres always gonna be popular boy groups. Groups like TVXQ, Super Junior, BigBang, and EXO were big enough to keep kpop alive and strong. They didn't need to be as global as BTS.
Girl groups though need a "Nations Girl Group" to carry all girl groups. Without a SNSD or Twice you are stuck with 50% of kpop just trying to keep their heads above water.
And please don't lie to yourself saying Aespa is the next NGG. They are not designed for that function. They will only be about one step above Red Velvet popularity. And Red Velvet were not even close to being NGG.
I'm not a Twice fan. But I understand their importance. I hope they resign.