I do agree that the whole crackhead subplot was unnecessary. If you want us to relate to these characters, they need to be relatable, mostly average people with jobs and normal every day lives. Then show us how something such as a virus outbreak that reanimates dead people into mindless rotting cannibals would really start breaking down society as it becomes impossible to contain and go from there. Adding drama in the shape of a drug addicted relative that lives in the streets seems distracting.
they went with the dug addict story line for Evil Dead remake as well
And if you understand why they did it in Evil dead, then you understand why they went with it here as well lol