You know, I just realized. Levi-tan being a deadbeat mom is why she keeps failing. If she can take the time to purpose-craft two resonators, she can take the time to actually raise them to be good vessels/weapons. But because she didn't, and left Carty to be raised by loving parents (even worse, cuz Levi-tan intentionally fabricated the memory of loving parents for literally no good reason) and now she's dead in a ditch because she couldn't be assed to be a mom for a decade or two.