To my ear, they all sound about okay for 4 seconds, until my brain recognizes that there's no tension being built or story being told. It's like every track is 4 seconds of music followed by 4 seconds of music followed by 4 seconds of music rather than a track with a real sense of progression.

Many have said in this thread already that maybe we ought to expect that a ml approach in the next few months/years could be much better. I'm not so confident that it will happen so soon. Audio might end up being a much harder problem than visuals, for a variety of different reasons. Having the time domain built into the medium requires some concept of memory, and even modern neural nets seem to struggle remembering what they said before the most recent prompt.

Once again though, its not impossible. Just requires the right techniques and enough people focused on it.