Even when looking at groups where the members are all vocally talented, like mamamoo and aespa, there is still no perfect line distribution. And it is an ideal that kpop Stans should not be even trying to pursue, since singing ability does not equate to having the right vocal tone that complements the song best.
And more popularly, asking for more lines, I know it’s extremely difficult seeing your bias in a particular group having basically zero lines, especially for larger groups, I Stan winwin ( that has at most 5 seconds of just saying alr alr) but you also have to admit that not all members are equally capable, and if winwin sang 39% of a song, it will not be enjoyable at all. I am sorry but my boy can’t sing, and it’s time we move on and accept that.