Hitstun doesn't last that long from boomerang for that to be possible.
Totally agree with the sentiment, and no, it's normally not possible... except if you're on a flat stage and chuck it at a space animal at relatively high percent (while on the ground and rethrow). Their higher hitstun would make it possible to juggle them with the 'rang for about 2 hits max starting around 90%. But yah, other than that it shouldn't be possible on any other characters for the most part. Don't think this calls for a nerf though, that's just the space animal struggle of play hard and get punished hard.