@SunsetSeeker
I will preface this by saying I did have my own thoughts on the arc beforehand, much like yours, I had thought that ice Kaguya was a poor addition, and my rebuttal, like your initial criticism was one mostly based on no prior thought and mostly emotions (I base that thought on the fact that you were cussing and were rather heated in your initial criticism).
Now, the arc actually happened because Ice Kaguya (all the Kaguya's because how she puts it, "they're both real", both since she has only revealed two sides of Kaguya, the "Kind" side and the "Ice" side) had gotten heated that the other Kaguya's had little to no regard for the future of Kaguya as a whole. There was the more emotional reason of "I want to be kissed by the president", which by extension is "I want the president to love me first", she was mad because the other Kaguya's had prematurely confessed themselves (the kiss) and as such this ruined Ice Kaguya's whole idea of being in love. This holds true because it is a much nicer way of the original plot of the series, making the other confess first, even if feelings are apparent, and Ice Kaguya makes it clear this was her reason on ch 141 and how expressive she becomes about the other Kaguya's not so much being honest with their feelings but not understanding the basic concept of the "right" moment to open up.
As for the second part, where I mention that neither of them needed a mask to fall in love, it could, arguably, be said that Kaguya was wearing a mask, however it has been the mask she has had since she was little was forming the mask. In ch 146 this goes into further detail with the progression of such a mask, at first being an educational one, based merely on her being told to act that way because it was the "right" way to act. She learns to be scared by people however, blaming both herself and others for the circumstances of her life. As such, even the Kaguya that Miyuki meets is one who is deliberately dishonest, she paid no attention to Miyuki because she hated people, and was taught to use them and manipulate them. This is why someone like Miyuki who disrupted this for a small amount of time by getting ahead of her in the exams, in 146 she doesn't state that the reason she fell for him was for hard work or intellect, when she confesses she fell in love it's of a scene where Miyuki is getting her ribbon from the pond. Miyuki had worn the mask meaninglessly, meant to get her attention but it was not even that that made her fall for him, it was not his intellect like I said but an act of kindness. Miyuki nor Kaguya needed a mask to fall for each other, I would maybe say that they needed a mask to acknowledge one another, however not to fall in love, because they fell in love in spite of their masks.
Lastly which I would say is your weakest point, that it was a lie that Kaguya wanted to love Miyuki for who he was too. It was one chapter ago that she admits this explicitly, and in this newest chapter too, she says "it doesn't have to be perfect", the entire facade of Miyuki underhanded in one sentence. The example of her losing interest because he lost his eye bags is a bad one, merely because eye bags can have absolutely nothing to do with hard work. This'll be easily criticized too but his eye bags could be some other issue, such as just a poor sleep schedule (we know this isn't it but just wait a moment). My point is that it was purely an appearance flaw, and I would be one to say that the chapter where she stops liking him for his good sleep is a comedic one, if you disagree, read the chapter afterwards (I think) where she is extremely sexually attracted to his horrible bags. If you'd like to bring up another instance where Kaguya didn't like him for who he was please do for I don't remember any.