If you play Slayer exclusively, then yeah, above 1 or below one tells you if you're above/below average.
If you play a lot of objective games, then it doesn't mean anything. A high K/D could just mean you're boosting your ratio and not playing the objectives, and having a low K/D could mean you're one of the people who actually want to play objective games for fun and not to boost some online stat so people can be impressed when they look you up or something.
Personally, I only really enjoy playing Slayer since it seems most people don't actually want to play the objectives. So my K/D is like, 1.2 or something.