I could be wrong, but from what I understand, the Quran is the final word of God, and Muhammad was the last prophet. So what Islam is, and will always be, was set in stone in the 7th century. It can't evolve like other religions. As with other holy texts written long ago, there may be parts of the Quran that encourage things that most of us in the modern world see as barbaric. But as the Quran is the literal word of God, bad people can justify doing whatever messed up shit they can find in it.