i mean, that's not 100% true, there are many groups that struggled but still managed to become successful in the end - take exid for example. back when they first debuted they weren't doing that well and barely anyone knew them. they were lucky enough that one fan recorded a fancam of hani performing up&down that went viral on korean social media - so much so that some music shows invited them to perform the song even though they ended promotions a few months earlier (they even got their first win for up&down). another example - hun and gon suffered SO MUCH bc of yg and right when we thought all hope was lost, they debuted in one of the hottest rookie groups this year. (woong too tbh)
this might sound harsh, but i think too many young koreans dream of being an idol - it looks really cool from afar, but it's not an easy job, and considering how oversaturated the market is, it's really hard to make a name for yourself. the sad reality is that unfortunately, hard work doesn't always guarantee success - there's just no way for every kpop group to be super popular, no matter how hard they work, because there's just so many of them.
besides, it's not like the groups that are the most popular rn achieved it without any work and suffering. just because they're successful now doesn't mean they haven't had their struggles in the past - i personally know many people who immediately assumed that bts were as popular as they are now from the start, which is so not true...
ps. sorry for the rant hskshkvskv i got a bit carried away... it just makes me mad to see how cruel the industry (and the public) is, especially now that most new idols are literal children, and not be able to do anything about it