It's about the imperfections. Someone once told me 'an empire is only as strong as its weakest member', and I think this movie for some reason really showcases that.
The batch 89 were the worst of HE's creations according to him, but they were the only ones with exactly what he sought. Ideas, hope, dreams - and more specifically, imagination. Rocket's brain might be what HE is seeking, but the truth is, he killed all of the results with that capability.
Because none of the creatures the HE created after Rocket and the batch 89 were personal. They were mass produced perfection, copies of copies of copies. Their sentience was carefully constructed by someone else - and so, they don't have what Rocket has. What the Batch 89 had.
Because the Batch 89 was a series of accidental successes. They weren't programmed. Their minds came out of nowhere.
Each of their imperfections molded them into what they were. Molded their personalities and hopes and dreams. Each one so miraculously different from each other. Every single one of them so incredibly flawed, so completely fucked up- and perfect.
Lylla chose her name because it was pretty and she would need one in the new world. Teef thought his teeth were the biggest there was and named himself after it. Floor liked to hop on the floor, so she chose it as her name. Rocket had a dream of taking them to a rocketship and fly towards the sky.
Hope, humour, comfort, dream. The four things one finds in a healthy family, and the four things that keep people from going insane in trying times.
They had nothing but each other- so anything was good enough. They had everything and nothing. They were the weakest members of HE's empire, and that was their strength. And in killing them he destroyed the very thing he sought to create.
Sorry for the rambling. Yes I'm still crying.