this has been done so many times before.

anyway.

he has a point and a purpose.

just think about it for a second. first, he uses kujas desire to die as a reason to end existence which adds something new to the bad things kuja had done.

also, kuja saves them after the fight with necron.

i could say more but basically. if you take necron away, it just doesn't work. they'd need to seriously alter the story to make it work.