I don't know but I think blaming supports only happens in lower MMR. If you are in high MMR, you rarely ever see people flame support for feeding or being underleveled. They flame if you make a bad move or something, but that happens on any role. I also don't see full carry teams all that often in high MMR. People tend to pick after what is needed. If someone calls mid, very rarely someone else will pick a mid hero. If someone picks a carry for safe lane, very rarely will you see another carry being picked so it ends up being two carries on one lane.
It does not happen in high MMR. Just play yourself up from your lower MMR. It is not impossible. If you believe you belong in high MMR, you should have no trouble getting there to be honest.