I don't know how ethical it is, but it's so mutated by the time I put it on YouTube; who knows? It's new territory.
I'm going to pretend "ethical" and "legal" are the same thing, but obviously they aren't.
Is this really new territory?
Artists have forever been copying other artists, but changing enough elements so that they can't be sued.
That's what you're doing here. The main difference is that the lyrics are still held under your copyright, so other people can't just copy your song wholesale.
But... they could copy your
melody, since even after your changes, you still don't have a copyright on it - even if it's a pastiche of AI melodies.
Whether someone would
know that the melody was AI generated is a different matter.