I don't know if its true about the author rushing the ending because of family matters. But I agree that it was clearly rushed and its pretty obvious. Everything was just way too set up got a good ending. The thing that really annoys me is how they handled the future. Most of them just got married out of no where. There was no growth with their relationship. Take Nezuko and Zenitsu, I get that Zenitsu liked Nezuko but come on he liked every girl he saw and Nezuko showed no interest at all, until the part where they talk about their dream person. They show that Inusoke had a child but with who? And the way they handled the reincarnations. They barely even changed from their past lives. The way I see it for now since theres no good reason, I believe none of them got married with each other. they all passed away and got reincarnated to these versions we've been given.