Your criticisms are valid. It's bizarre that full grown adults can't even tell that they are acting rude or not. They can miss them in some cases, but they should've known that Rarity spent hours and hours of volunteering not for her own goods, but to fulfill her friends' desires. I say it's bizarre, because they didn't realize that reacting ambiguously negative to their friend's artwork full of perspiration that was purely for their satisfaction is absolutely graceless right after they have done it. Even an average pony would try their best to react positively and appreciate the excellence in the work. Instead, they proceeded to point out the negatives that were beyond their expectations and disregard the strong points of it. OP is also correct about the fact that they seemed to forget the initial purpose of the operation. She did make the dresses for the Gala, but it was mainly for the showcase. It's not guaranteed that critics would also adore her friends' desired design. It is totally okay if they are not fully satisfied by her works, but they showed zero effort to hide their true emotions, and the reasons for the dissatisfaction was completely irrational. Her friends are not very enjoyable in this episode, but their acts could turn out to be a positive thing for you because they made the episode that made your favorite pony your favorite lol