How losing with high kda affects your MMR?

I've been in the same situation multiple times: trying my best, winning my lane, having "good stats" and trying to help my team (roaming, ganking if jungle) as much as possible, and still we lose the game. In this situation (having good scores etc), do I lose as much MMR if I do when losing with bad stats? For example: Losing with 8/3/6 (200 cs) compared to 3/9/4 (70 cs) or something. How does these loses differ from each other? And can I EARN MMR when I lose a game with good scores? IMO, the MMR system could be more player based than its atm: scores->wins/loses, cus then there would be less stress and less "I must to carry" -players in low-elo, for example.
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