People ignoring their role; Why this was destined to happen and why it's bad to support it
While it's true that most people have one or two main roles... even in those scenarios if you are able to counter pick the enemy team with a tertiary role, it is almost always preferable to do so. In a ranked environment you want to stack the deck as hard as possible in your favor rather than squabble over petty nonsense like "UR THING SAYS MID/SUPP WHY U GOING TOP WTF REPORTED".
Not only is this predictable, it was impossible to avoid/destined to happen. Even if this is not specifically the case in all instances, in other instances you might want to synergize with what someone else picked, for example a person might select Alistar and someone that had Top/Jung might say "Hey that would go well with my Kallista" which will then infuriate the guy that had "ADC" as his primary selected role.
My point is; The system was doomed to fail, gg.