I figured out the one improvement that would have made Wall-E worked even better for my taste. They totally should have "Charlie Browned" the people (in other words, their dialogue should have been unintelligible to the audience and their faces would not be seen). There were ways to tell the story without that. The Wall-E and Eve parts are what drive the film. I still love the movie. I just think that could have bumped it up my list to second rather than third fave.
I see what your getting at, and I could see it work... but then the real message of the movie wouldn't have had the same impact. To me, the movie was 2 messages. one about the romance between Eve and WallE, and the not so cuddly second one about how putting off Earth's probles until tommorrow is dangerous, as tommorrow always comes.
And when I first heard about the 400 pound humans with melting bone structures, I thought they'd be horrible monsters. And they turn out to be actual relatable humans. The fact they are relatable and personable turns the message into a freidnly warning, and not a Captain planet style Scared Straight approach.
I think all the scenes with the captian finding out human's folly, and discovering what he's been missing his entire life is one of the best parts of the movie. And his heroic actions spoke to the character and the audience. You CAN change things. it's not easy, but it has to be done.
While I could agree with you that it would work well without the dialogue, it just wouldn't have that human emotional impact that makes it relatable.
Though I do think they explored that concept early on.