I think that Mugut's bad behavior is being used here to show that outwardly appearances don't make a person. It's the genteelness that is important.
What's the point of being the greatest businessman if you don't even have the decency to talk with dignity to others? (Let alone your wife.) And that is why, Kaumudi's changing a saree is not going to make much difference. Yes, it will make her look pleasant and Mugut will like it (precap) but it will take more than a saree change to turn Mugut's deep seated resentment against his wife. Kaumudi has spent years being told that her lot in life is to be a good wife - and that means taking care of her family. Being a good DIL, exclusively. Her mentality has been such that she has not been allowed personal freedom. Her being comes from being to others. This is a difficult mindset to change. This is what she needs to do. The guilt that is associated with freedom for the self and doing things that you are happy with - that is the right of every person, Kaumudi does not know that. When she does, then everything will fall into place.
Both are correct in their thinking in the circumstances they find themselves. However, instead of facing the challenges, they have let satus quo - I'll be the long suffering husband and my wife is ignoring me so I am allowed this adulterous freedom/I am a good wife and I will look after my family and be the best DIL because that is what a good wife means - determine their lives. And this is the outcome. Things had to come to ahead, after all, how long can it go on like this. Both are oblivious to each other's feelings.
Now they will have to re-learn to be together with each other. Whilst Indian mentality would never allow for the woman to seek pleasure outside the home, it deems it OK for the man. This is a double standard, and I think the show is trying to expose this.
(Think about what would happen and how lenient this family would be if Kaumudi was having an affair.)