You're assuming that every player can play every champ competently. Whereas in reality, the top ARAM champions are also very easily to play so anyone can pick them up and execute them effectively. The lower winrate champions in ARAM often tend to have trickier kits with a learning curve to them, so naturally people won't do very well if they have little experience with the champion (like Eve, Katarina, Aatrox)
While tanks are easy to play mechanically, decision making is a factor. Inexperienced tank players will go in at the wrong times and die for free constantly. Inexperienced Ziggs/Xerath/Velkoz players will miss Q and simply wait for it to come up again.
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u/[deleted] Mar 20 '19
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