I'd say many features of string theory don't mesh with what we observe in everyday life.
Brian GreeneString theory is the most developed theory with the capacity to unite general relativity and quantum mechanics in a consistent manner. I do believe the universe is consistent, and therefore I do believe that general relativity and quantum mechanics should be put together in a manner that makes sense.
Brian GreeneHow can a speck of a universe be physically identical to the great expanse we view in the heavens above?
Brian GreeneWe're on this planet for the briefest of moments in cosmic terms, and I want to spend that time thinking about what I consider the deepest questions.
Brian Greene