It's not a garbage stat. Any singular stat is "garbage" if that is the only thing you look at.
At least other stats by themselves can give you some information (ie a high FG% means the player shot well). A high +/- says nothing about the individual player's performance.
except for Hayward. Who am I to point out the hypocrisy of other fans. But, I saw posters trashing Favors, Burks, Exum, Lyles, and Hill.