[spoiler]I believe that it’s merely an error in the storywriting. EVE is supposed to be a new, advanced robot (and it’s very apparent that the technology went into making her is different, if one recalls how her circuitry glows while in the Repair Ward, while WALL-E has a more modern circuit board [random note: I suspect that either WALL-E’s circuit board or one of the three that EVE tried to offer him can actually be found in an old Mac computer–it would fit Pixar’s love of easter eggs]), and yet, as pointed out, not only are there no advancements being made on the Axiom (by the way, if they compact and throw away all their trash, where do they get any raw materials to keep going for 700 years?), and yet, as also pointed out, EVE and WALL-E had to have been made at approximately the same time.
The paradox suggests, to me, that the storywriters wrote themselves into a corner, or simply didn’t notice the inconsistency.
Another possibility is that scientists continued to advance for at least another generation, before people began to forget the importance of education (and life). Look at EVE’s ship; it looks far more advanced than the Axiom itself. Sleek, gracefully-shaped, while the Axiom, while clearly having very powerful engines, has a much rougher design and looks to be made up of a bunch of metal plates (the seams of which are visible). It’s possible that the captain of the Axiom, about 30 to 50 years after the beginning of the cruise, remembered their planet and ordered the construction of the probe vessels/droids. Maybe EVE had been already designed from the latest technology, but it seems inconsistent that she would have been built at the same time as WALL-E, as her technology has at least thirty to fourty years’ advancement (compare our modern microcircuits with old transistor systems).
Another suggestion of improvements since the Axiom’s launch is that AUTO himself understands how to use a book, while the Captain does not. This means that AUTO has seen a book used before, so the Axiom must have gone paperless since its launch (or, in any case, books ceased being used, which means that there were some advancements at first, while it still -was- being used).
Bottom line, I think that if the storywriters noticed this problem at all, they probably left it just so people like us would figure it out for them. Most people wouldn’t notice.[/spoiler]