The opposite problem of not leaving enough lose strands I think is that everything ends up feeling like a Chekov's gun. This is a problem that many mystery novels and dramas/romance suffer from. Like when everything including the characters act in order to keep the plot going forward in the direction that the author wants it breaks the immersion of the reader and ends up feeling like emotional manipulation in dramas and romances especially if they are also tragedies and the author is asking you to feel sorry for the characters. Sometimes some things should be there even if they will have no large significance in the stories of the characters so that the world doesn't feel like a fake-setting built around the characters who themselves feel like puppets of the author. An exception of course could be made in stories like Steins; Gate where everything needs to be(or at least needs to seem like it has been) set around the actions of the characters otherwise it will seem retconned.