Everyone seems to understand the progress theme by now, and even the people who didn't at first have had it drilled into their skulls through endless discussion, but what people miss all the time is something that was obvious from the first episode.
The faces of the robots. While progress was the theme, individuality was written to be a part of progression. This isn't anything amazing or hidden, but I think it may have been too subtle in a show where robots are throwing galaxies at each other.
Everything was personalized, They stole other robots, and morphed glasses and their gang logos on to them. The Daiganzan was different after Simon stole it, Kamina city was built on top of Teppelin, Simon's version of the CGGL was different from Genomes, and the villain of the story who stood against progress was someone without individuality at all. He was just a blob who looked like everyone else.
I don't have anything to say other than it really sucks that a lot of people don't seem to get this. This kind of plot hasn't actually been done before. It's great that people recognize that GL tips its hat to the classics through references, but people ignore the unique things it did.
Sorry for the bad grammar. It's late.