Deaths do NOT (besides the plain ol' feeders n shit) equal a bad player. It might just mean the other team was better. What does matter is what you do while alive. I don't care how many times you die, as long as you are helping secure kills, objectives, or other.
Also if ration had anything (it is probably very little) with ranking, then riot would pretty much be saying "Fuck every support main."
As this game is complex, I doubt they half assed the ranking system. It would look bad on their part. So the amount of variables could be really large and refined. As example (exaggerated), how long it took for your first death.
Tl;dr Everyone is being too narrow minded about the ranking system.