I feel like it's because with season 3, there was nothing to show. None of the characters were the same, but at least the other characters had some vague direction. Dev has hd that same clueless expression from episode 1.
Shaheer is a master of his craft, and given the space and material, he can make magic. In season 1, he had that. Season 1 Dev was so beautifully complicated, a product of circumstances, a hard working businessman, a doting big brother, a baby to his mother, and someone that fell so completely and irrevocably in love. We really grew with him in season 1, we felt him open up slowly, experience love and all the joys that come with it. We saw Mr. Obhodro laugh for the first time, we saw him completely in awe of Sonakshi's strong values and character the same way we were in awe of her. We saw him ruthlessly wrecking people's careers, and while we didn't agree, we understood.
Dev was a such a layered, complex amazingly written character, that Shaheer had so much space to make it his own, Dev 3.0 is a confused clueless joke. He just walks around stupidly without reacting to any situation, how can we expect shaheer to add anything to a character that is so hollow?