Anything works on all characters if your opponent is ****ty enough. Charged projectiles like needles are particularly susceptible though. Other projectiles with a long cooldown like the boomerang or pikachu you can also hit with a decent read though. But faster projectiles like mario's fireball or lasers? You either need a hard read or your opponent has to suck/screw up. In all cases though, flip kick is not difficult to avoid. Put it this way, how often do you see Nairo or Choko kill with it? Not very often. The vast majority of their kills come from aerials and up special because flip kick is just too punishable and too readable.
I'm not saying it's a bad move, but against decent defensive players it's primary utility is in recovery and defense, and it's offensive use is situational at best.