Seuss wrote three kinds of childrens' books: those designed to help them learn, to teach them how to be people, and Green Eggs and Ham The trouble with expanding his books to fill 90 minutes is that the "how to be people" books are the only viable source material (although Terry Gilliam would probably do just fine with Green Eggs and Ham), and it's literally impossible to maintain the spirit of those books for that length of time. The Grinch and Lorax were never meant to be explicitly funny, they are dramatic although whimsical tales written specifically to promote s moral. A critically well-received feature-length Grinch/Lorax film that held true to the tone and message of the originals would inevitably reveal the socio-political statements behind the message which Seuss deliberately chose to make obscure--even if the film didn't stray outside the original message at all, just by staying on the point that christmas isn't about material goods for 90 minutes would turn it into a movie about the commercialization of christmas. And while that is absolutely the driving statement behind the book, to make it the forefront of the story would be an even worse violation to the spirit of Dr. Seuss than the Jim Carrey edition--not that anyone was concerned about maintaining the spirit's integrity when they capitalized on a christmas story against capitalizing on christmas--because it wouldn't sell, which I understand is counter-intuitive.

His books are profoundly calculated to be always present in the lives of children, his books are so incredibly made for children that they inherently applied Chomsky's ideas before Chomsky, ideas that nobody began to take seriously until 1980. Seuss wouldn't have known the scientific reasoning behind his techniques, with psychology where it was and psycholinguistics where it never was at all it's possible if not probable that he never even related his implicit understanding of people, words, and design to any notion of science at all--he was probably just really fucking good at making propaganda, which many may know as a factoid of interest that he produced WWII propaganda, it's not very well-understood how pervertedly and obsessively precise and complex propaganda must be in order to successfully manipulate the desired response out from as many demographics as possible, let alone in manipulating simultaneous but different specific responses from different specific demographics. And when people learn that he used to do propaganda, they don't really connect Theodor Seuss Geisel to the person they know as Dr. Seuss and don't really think about the fact that he was so good at manipulating people that the US government paid him.

Not to imply that there's anything insidious or harmful about his books for kids, only that they are multi-layered designs meant to be accessible and relevant throughout the entirety of early childhood development, as to be read to you and by you repeatedly throughout your development while providing multiple significant and novel experiences from within a single book as your further development allows you to explore progressively further layers of the book. You don't even have to be aware of what a book is to be into it, infants fucking live for rhymes and patterns in sound--something that was only recently accepted. If you can"t read yet but are able to focus on a book, it happens to be extremely stimulating visually--so on and so forth up until you end up reading it to someone else. That they can be enjoyed by anyone at any point and have the potential to be experienced as new several times over makes for a very popular and unusually memorable design, as you might have three separate memories attached to the same book for each time you discovered something new. And so whatever morals Seuss thought would make us better people end up being cemented into our heads without ever realizing that we can't remember a time that we didn't know How the Grinch Stole Christmas.

While most of Seuss' fables have statements behind them, those statements are not the "truest" form of the message Seuss means to convey. The Grinch book does not attempt to explain the commercialization of Christmas or why it's wrong, because the book is specifically for kids. It just quietly plants a small seed that differentiates material things from non-material things. If the Jim Carrey version did that to any degree at all, it'd be a much more accurate rendition than anything that wouldn't be immediately accessible to a kid.