I dunno… I mean, Princess Tutu was actually supposed to be longer, and I think in the original plan Ahiru was going to find a way to remain a human girl.
But the thing is that… well, that whole ominous “accepting fate=happiness, defying fate=glory” was actually proven wrong in the end. They defied their fates, and it was glorious, but it was also… it was joyful. It wasn’t perfect, there were bittersweet bits, but for the most part it was an ending filled with hope and the expectation of a better future for all the characters involved.
In homestuck, we had that moment where it looked like Terezi was going to defy fate in a big, awesome way, and then John half-assed it for unfathomable reasons, and the end result feels like a rain of spittle in your face and you can’t tell whether any of it was what Terezi had originally intended or not?? Everyone looks even more deeply constrained in their roles, and things only seem to be going as intended on a superficial level, and it frankly looks like they didn’t defy jack fucking shit but just marched to somebody else’s tune, somebody who didn’t really care all that much about them