As I mentioned at astro’s: (spoilers)
I interpret Cat Soup as a Quest story. The difference between a Quest and a Journey is that the former has a defined goal; the latter can be its own reward. The flower in Cat Soup represents that goal – it is a symbolic one, which we can paint further interpretation on, but a goal all the same. Perhaps attaining teh goal is why at the very end, Reality itself was no longer required. I am reminded of the line from Hitchhiker’s Guide, about how the Ultimate Question and the Ultimate Answer are mutually exclusive – knowledge of one precludes the other, and should both be known, the universe would vanish to be replaced by something else even more “bizarrely inexplicable.”
I had thought the Flower only appeared twice, though, which is the bare minimum for a quest – tell the hero what is their goal, then show them reaching it. In actuality it appears five times, four at the outset and then again only once at Quest’s end.
Overall, Cat Soup lends itself to this kind of meta analysis but pushing any analogy too far is pointless; it’s deliberately vague, as the director’s commentary reveals.