And Pooja, yes it's true that Adi was not ready to be a father, but she never gave a second chance or tried to convince him. He had thought that she was trying to fool/scare him. She could have separated from him if she wanted the baby. Afterall she has his wife and his best friend, didn't even tell him that he messing up his and her life. Even after the abortion, after being not in love and just being a friend to him, or even when she fell in love with Yash, she could have come out clean.
Both Yash and Pooja, after having a physical relationship, continued cheating their partners knowingly. Yes we can't help falling in love, but you can be atleast be truthful to your partners and have decency to call it quits before progressing into a physical relationship and pregnancy.
Yes Aditya's and Zoya's immaturity and childishness can be the factors that distanced their partners. But that is not a valid reason for cheating.
Adi is broken up because everyone blames him for his broken marriage, him not being man enough to shoulder the responsibilities. The scene where he says to Arjun that I have grown up too much to have icecream broke my heart. He is afraid to be himself, he is distancing himself away from others because he doesn't want to be blamed again for being childish, for not wise enough to be responsible.