Like ShlupQuack said, it's not like the original is going to vanish from existence. It's okay for there to be multiple adaption of a book.

What's that, I hear you saying, a book? Mary Poppins was a book?

Yes. Most of Disney's stuff is just adapted from a book or folklore.

So maybe the aim of this "remake" is to adhere more closely to the book.

No one called Disney's versions of the two Narnia movies remakes of the BBC miniseries adaptations. Nor the MGM Wizard of Oz a "remake" of the 1921 silent film version. Etc.

Likewise, when there was rumor of The Neverending Story by Michael Ende getting a new film adaptation, I was all for it. I wanted to see all the stuff they left out of the book. And if I didn't like it as much as the 1984 film, I never had to watch the new version again and could still watch the 1984 version as much as I wanted.

EDIT:
ALSO, I would LOVE for someone with enough courage to take on The Wonderful Wizard of Oz by L. Frank Baum in a more faithful adaptation of the book. There was an anime version in the 80s that was decent, but I'd like to see what a nice dark live action version today would be like.