Indus Valley script

Why we cannot decipher the indus script ??
we may be close to it.

Maybe, maybe not.

Rao et al. say they’ve found evidence it writes a language (PDF):

But Steve Farmer et al. say not so fast (PDF):

If it is the Indus Valley script, shouldn’t they just assume the most common words are “like” and “totally”, and perhaps “awesome!!!”?