I don't remember book 1 all that well, having read it minimum of a decade ago. But I feel like Morn had a lot more of a personality in it. While, yes, she's

eaten up by addiction and trauma

here, it's like that's all she is. And there's minimal plot, it's mostly character-driven, so Morn's lack of character hurts. Slap a fresh coat of character on Morn and focus a bit more on the "hmm, what's up with these pirates, the UMCP, and the Amnion", and there's something really interesting going on (even if it remains mostly about Morn).

Also the physics was either distractingly bad or distractingly poorly explained.