I fix some. If it's a stuffed animal that I got for a quarter at the thrift store, I don't bother. But if it's one of the "durable" actual dog toys, I'll give it a shot. It's easy if it's a small tear with nice neat edges, I just close it up with tiny stitches. Sometimes they don't leave enough fabric to bind it back together, in which case I don't even bother trying to put on a patch or anything.
They actually put a tear in one of those giant Chuckit balls, the soccer ball sized one. I used a leather needle and leather thread for that, it was very tough fabric. Gotten another year out of that toy so far, although it wasn't easy.