It doesn't replace anything, it only explains what had occurred, not how it occurred. So, perhaps God still was responsible for HOW...
My wife is a strict "Seven Day Creation" believer. I tend to think that God took much longer; no sun and moon until the third "day", that kind of thing. But my main complaint with Creationist Classic is that our prime goal should be telling others about Christ's personal love for them, and his sacrifice that makes them clean before God so that they can have fellowship with He who made them. When well-meaning and faithful Christians lose this focus and drift off into the Creationist Cul-de-sac, it can put barriers up. Case in point, my best buddy from high school. He is an FBI agent, very intelligent, and very scientific. (Thank God he hasn't been lulled asleep by the Unitarians!) If she went to him, and banged him with "God made the universe in eight days and you are going to hell unless you believe it!", he would laugh in her face, and decided based on that sampling, Christians must be confused simpletons who don't understand a billion years of erosion, the background radiation of Big Bang, and simple math. Christ's free gift of Salvation, the real message, would be dismissed along with the weak (he would feel) argument of a seven-day Creation. But if I approach him with Salvation, which is centrally a spiritual argument that has no litmus paper proof, he may be argued around to understanding how God loves us all.
I could be wrong, and SevenDayism may be true. But if I am wrong, it doesn't threaten my salvation, God will straiten me out after I am dead, and then it won't matter. It will matter if I fail to reach my friend because his scientific mind locks me out based on what he considers foolishness. I guess the arguement for me would better be the admonishment "not to eat meat offered before idols" if it would offend my brother. It comes down to what the most important point of the Bible is, and I have to side with Salvation.
My $0.02.
It explains "how" by saying there is no need for a designer!! If just blind happenstance and mutations and survival of the fittest accomplished it all then what good is this god? What kind of a role did this idiotic deity play? This kind of god is superfulous and a deity without a brain.