Crappy grades from SuperHotIvy WILL NOT get you anywhere in medicine. If you want to be President on the other hand, bust your ass, get into an Ivy and then spend your next 4 years networking
Im not sure if community college would kill you if you got an diploma from a good state school (or private, or ivy), saved the hard BCPMs for the University and you came out with a high GPA and decent MCAT scores. Grades matter, MCATs matter, and most importantly, expereince matters. Name in and of itself is minimal.
That said, there are a few exceptions. Where it can make a difference is letter writers. If you go to Brown for example, and get a letter of reccomendation from the father of electrophysiology, who writes some impressive things about you, that could definately outshine someone who gets a very general letter from a bio prof anywhere else. Second exception is if you apply to the same school that you went to as an undergrad. Third exception is if you want to save fishing children in Angola, and your mid-tier school doesnt offer the oppertunity, where a top 10/20 might. Doesnt mean you can never do it, just means you have to look elsewhere for your oppertunities.
From the point of view of someone who attended one of those grade inflating schools, I had an incredible experience. I got a lot of freedom, I got to learn from incredible people, and I had oppertunities that many people dont have access to. BUT. I never took advantage of any of that until I graduated. The point being, dont bother with opportunity unless you're going to take advantage of it--and that goes for any school you decide to attend, not just the Ivys.
Don't get so stressed out. (I mean, prep for med school is salient, but it shouldn't be your life. Believe me, it only causes 1st year burn out) Good for you for having so much foresight, but dont let it ruin the experience