Besides giving string theory a bit too much credit for the idea of extra dimensions:
...with a review of Newton's theory, general relativity, old large dimensions, and warped dimensions, among other possibilities inspired by string theory.
which have been around since soon after Einstein published his general theory,
he seems to simplify things a bit too much. I'm no expert here, but the usual thing is that there's a parameter space of deviations from Newton's laws, one axis of which is the size of the extra dimension(s).
The Eotwash group has done some great work closing off much of this space, but there are still regions they can't reach.