I find it quite superficial to call the new movie a love letter just because a number of stills have similar elements in them.
As an example: In the water fight scene the anime has a LOT of story-telling with her actions being clearly based on high level moral motivations, as well as observations of and adaption to the progression of the fight itself. Every action taken has a reason and nuance behind it, based on who and what her adversary is as well as the tactical situation. In the movie it's a straight-up beat-down of an almost entirely unresponsive puppet.