I think he means that they don't capture the essense of the good Doctor's style. And I can't blame him. While this stuff does look good for CGI, it doesn't quite capture that drawing quality that is such a part of Seuss's charm. They can't emulate crosshatching or any of those sharp pen lines that make the books really pop. I mean, even in 3-D merchandise, it just doesn't look right. The closest 3-D counterpart was the Wubbulous World of Dr. Seuss, a Muppet production (and even then there was something off.)
His work is more suited to a 2-D medium, IMO. I mean, the Chuck Jones specials captured the style in animation form, but they were more like a cross bread between Seuss and Jones's styles (which are lovely together). The only thing I think that captured the style of the books dead on were the Depatie Freling specials. Those are just too underrated. Especially since Sesame Street songwriter Joe Raposo wrote the music for most of them.
EDIT:
As for the casting, I would have gone Steve Carrel as Horton, and someone else as Steve's part. But if it were up to me, it would have Rob Paulsen or Jim Cummings or someone like that doing the voice.