So I was rewatching Phase2 Bajaj scenes and I realised why Kuki Bajaj relationship is so the way it is.
Bajaj says to himself in the car I can never say how much you mean to me how much I love you Prerna & if we go back to phase 1, he said Prerna was in that 1% who knew him that's why she defends him explains his pov to Kuki; He though is at peace, he feels he won't be chosen over (--it's a decision that you have to make Prerna) which is why he doesn't rather can't say his heart's desire to Prerna.
On top of it, he knows Kuki being so close to Prerna would want to be with her only, since her childhood (which is why he married her at the first place yet for Prerna's happiness he let her go). To save Kuki from the pain of parental separation, he distanced himself from her and let Prerna take the lead. Which is why he stopped expressing his love altogether. 😢