Some of the best endings are open
If any of us were plopped down in the middle of this story, in real life, there are many things we wouldn't know or find out.
This movie had its biggest problem, for me, early on, with changes in residence and Sarah throwing off Kevin. She had her reasons, but we never really saw what they were, except for Kevin being kind of a doofus.
At the end, we left our characters as we would have in real life, with a life left to live.