The song just didn't suit them. I think they were trying to show a different side of themselves but all they showed was that they couldn't pull off a girl crush concept. Their voices and expressions (with some exceptions, of course) just weren't powerful enough so it ended up feeling very lackluster and a little awkward.

Welp,.......... gee.
Guess I must be the only one who actually liked it and hope they're able to do more of this type of stuff in the future.

Was it 'perfectly' done? No - there was a certain.....reserve to it all, yes, but I think that was more due to not having performed anything remotely like this before - changing styles can take time.
The one time I've seen them live, they were doing real airy-fairy type stuff, and while they certainly did a good job then, I felt like they were all either holding back, or *being* held back from giving a really gutsy performance.
If some of the other GG members' reactions were any indication (like, say, Mamamoo and Oh My Girl), this was a big happy surprise.

They HAVE the voices to be able to do something along these lines (Kei and Baby Soul and Mijoo, for starters), so I sure hope they continue their training and seek out something that's definitely different from their 'usual' or 'standard' fare - just because GFriend's experiment with "Fingertip" didn't seem to catch on, trust me, there's a lot of people out there who sat up and took notice and wanted more like that from them.
Same thing here with Lovelyz.

<3<3<3<3