Though his only previous Broadway appearance was in the 2017 revival of Arthur Miller’s “The Price,” Danny DeVito commands interest without having to do much, and rewards it with funny readings of even unfunny lines. Yet despite his likability, the only parts of “I Need That” that feel authentic are those, near the end, in which the nonissue of Sam’s hoarding is momentarily swept offstage to make space for a few minutes of real father-daughter drama. To this, the DeVitos bring a vibrant understanding — part pride, part dismay, all mess — of what it means to be related. Sometimes what’s neat just isn’t as compelling as what’s not.