It's an okay stat if you give it a very large sample size, such as an entire season, then compare it to, say, someone on another team in the league with a similar amount of games played and similar deployment. The difference also has to be significant. Two fourth line centers who finish at -8 and -12 each don't have a significant difference between the two. If one is +10 and the other is -20 though, that tells you a lot. Even then it won't tell you everything about each player. There could be a valid explanation such as the one who finished -20 being on a terrible team. However, just because it doesn't tell you "everything" doesn't make it a meaningless stat in my eyes. It has some applications, and however few they may be, that makes it not meaningless, by the definition of the word "meaningless."