Honestly, can't other characters set up similar situations to the Fukua loop with the right assists anyway?
In retail, Fukua's loop is netting 3.2k (c.lk, c.mp, c.hp, c.lk, c.mp, c.hp, m shadow), but with Bella and h osiris I can get 4.5k off of a similar setup midscreen (c.lk, c.mp, s.hp, runstop, c.lk, c.mp, s.hp, mp lnl+osiris). In the corner I can make it pull them out of the corner (c.lk, c.mp, s.hp, runstop, c.lp, c.mk, kanchou+osiris) for 3.9k. After the osiris I can air grab, hit left, hit right, go high, go low, s.lk to catch buttons, or burst bait.
I feel like the question is really less "why should every character except fukua etc.", but "is it okay for characters to use assists to make loops, and if so how good can the loop be before it's too good". Because if this Eliza loop is fine, I don't see why the Fukua assist creating a similar loop is not okay.