you are viewing the success or lack of success in hindsight
hindsight is 2020
Of course it is. But have you ever heard the phrase "those that ignore history are doomed to repeat it".
I can use the success and "pre-success" endeavours of the groups to ascertain whether KIOF, if given their PAK song, will flash in the pan or maintain the success. And yes, some of it will obviously matter about followup songs.
But given their footing, the way they are marketed and how they are growing their profile, even without that national hit song, i can easily understand the OP's designation that they will ascend upon getting that song.
I remember people saying the exact same thing about Idle in 2020. Literally the same arguments, both for - Idle need one massive song to really get into the top tier, and people like yourself going "oh we've no idea it could be anyone".
Lo and Behold Idle got their massive hit and have stayed in the top tier since.
even Gidle in their recent comebacks have had their TT perform slightly less than before now - Mamamoo even more so (I'm not familar with Mamamoo's heyday but when was the last time they had a hit song) - all good things must come to an end the question is whether it's after numerous hits or one
Gidle are now approaching 7 years old, have had 3 PAK songs in 3 separate calendar years, and are possibly going to just get clipped for a Daesang by a massive hit by Aespa.
If that's still not top tier i've no idea what to tell you mate seriously.
Yes MMM have dropped off but they're now 10 years of age, and focusing on solo activity. Infact, the literal fact that 4 people from a mid-tier label can all maintain lucrative and reasonably good solo careers IS the evidence of how they've achieved lasting success.
I'm not immune to your arguments that you can't know the future, but to be frank if there's any current group that's like MMM and (G)I-DLE, it's far and away KIOF. And that bodes well for their future.