The characters in one serial should not have any affect on the characters in another serial. Amit and Shilpa play husband-wife in one serial so what? That doesn't mean that them being son-in-law/ mother-in-law in Kkusum needs to be frowned upon. They're actors, it's what they do. They play different roles and they can't always fit the picture-perfect outlook on what is expected of them. Accept that this is how their characters are in Kkusum because it's not going to change.
Kumud and Kshitj were appreciated as a couple by their fans. Ekta is a smart woman; she knows what needs to be improved on her Kkusum serial to make it run. That's why she brought Kshitj and Kumud back as a couple in the show.
As for Kshitj dying, what alternate planet are some people living on? He is one of the foundation actors- he holds this show together with others. Why would Ekta want to ruin that? Most of the viewers of Kkusum adore Kshitj as an actor, as well as in the Kshitj-Kumud pair. So leave well enough alone. 😊