This is kinda about Lightsum (people commonly say about Lightsum that half the members look cute and half look girl crush so the group looks awkward.)
On one hand, 1. people can completely change their image with a new hairstyle or makeup
2. even if they can't, I think most people care more about the song than whether the members seem suited to the song/group.
However, on the other hand: people judge really quickly from 4-5 seconds, and get a bad impression really quickly. For Lightsum, if people think the group doesn't look cohesive, it could lower the strength of their brand vs other cute and bright groups like ILY:1, Twice. Just from a first impression.
So personally I think it does matter.
But with Lightsum I guess Cube was in a difficult situation because they had to debut Chowon who looks tough but they also had to debut Nayoung and many young trainees.
There's nothing wrong with Lightsum though, if you just watch a few seconds of their MV. But I think when watching the group perform together, and actually seeing all their faces next to each other, is when it feels like the members don't fit together.
BTW I tried to pick these photos unbiased (pictures where they all look good)