Makes sense now that I think about it, the groups that debuted during late 2017-2019 didn't seem to belong to a clear cut generation. I guess 2019 can be considered early 4th gen if we want to push it however there's no way 2017-2018 groups can be seen as rookies.
Groups that debuted from 2020 onward are in an unique situation due to the pandemic, that's what makes them different from the previous generation imo.
YESS!!! 2020 GROUPS FEELS VASTLY DIFFERENT FROM THOSE BEFORE THEM. The pandemic has changed KPOP forever i think