Dont get me wrong. It doesnt mean the kpop groups are not versatile, but they have limited room to be versatile while maintaining success (at least in Korea). This is also not a bashing post, as I am casual listener of the following groups, else i wont know their progress.
Some of the examples:
1) Twice - all cute and bubbly songs did well, and their darker songs aren't being received as good in korea (saving grace is they get more success internationally)
2) BTS - their upbeat songs are received better than mellow/slower songs
3) Blackpink - their hardcore dance tracks are more popular while other types (Ice cream, LSG) are less well received (but still chart decently)
4) gfriend - charted so good until change concept with Fingertip, after that managed to regain some fame with old concept but continue to fade after that
5) red velvet - this is a bit tricky cause over time thr GP preference shifted from their red concepts to velvet concepts.
Compared to the past
1) SNSD - bubbly songs did well, changed to mature concept - the boys, i got a boy, lion heart all did well
2) big bang - needless to say. Their mellow and dance tracks have equal success (eg. Bangx3, fantastic baby vs blue, loser etc)
3) 2ne1 - same, their ballads and dance tracks are well received
4) sistar - summer songs and darker concepts are performed equally good (but more inclined towards summer)
These are just some popular examples.
What has happened to the korean music industry.
The only one who is able to be versatile is (G)I-dle thus far. Even newer groups like ITZY is sticking to one consistent sound. Why is it like this? Is the industry being oversaturated that people are only looking for certain groups for certain sounds and once they deviate, they lose popularity?