It was a bit odd that this was not simply live-action, I would only note that the scenes set in Limbo would have been a VFX challenge back then. Not to mention the scenes of the villain's mayhem and destruction.

I'll agree that Cusack doesn't pass the, "What does Brad Pitt sound like?" test, but neither does Meg Ryan. As it relates to the animated vs. live topic, perhaps the realistic human characters just needed realistic human voices? If it had been live, I'd call it perfect casting to their types. Also, these names are big enough to signal adult ticket buyers that this was not some shabby production.

He was working with a studio with no animation experience which wanted to get some of that Disney business, so threw money at him. For contrast, listen to the commentary on the film Titan A.E.. Bluth is rather open on the why's of that film's problems.

Favorite exchange:
"This makes no sense! Why didn't we do a scene to correct this?"
"We ran out of money."
"Ah. Right."