Yes, it matters because it goes against LCMS teaching.
That's not strictly true. LCMS teaching is more nuanced than that. The LCMS believes in an inspired, inerrant Bible, and most traditional interpretations of that Bible.
Therefore:
1) What you think about the origins of life does not determine whether you are saved. Both creationists and evolutionists can be saved.
2) What you think does not prevent membership in the LCMS. Both creationists and evolutionists may be members.
With that said, most LCMS pastors favor YEC. Just keep in mind that what pastors think about the origins of life is not the same as the theology of the church. The job of a pastor is to preach Christ, not teach you science.
Next, make sure you get your science correct. Science doesn't make truth claims. It presents what it considers the most probable model, and there is an important difference between that and claiming truth. Further, evolution says nothing about the age of the earth or life's origins. Those two issues come from geology and abiogenesis respectively. What you'll find on the Internet constantly misrepresents what scientists are actually saying, and what the Bible actually says (at least per the LCMS view).
With all that said, if you do manage to remove the clutter, there are still differences between what science says about some things and what the traditional interpretations of the Bible say. But it's hard to have a good conversation about it given there are 1001 views all arguing different ways to resolve the problem.