that whole argument stems from counterpicks and their potency.
lest take
as an example.
cant touch
in any situation whatsoever, just loses on champion selection.
however the reverse is also true.
has nearly no hope against rammus.
riot likes to promote "every champion can win with skill" but thats nonsense. there are unwinnable situations, they do exist, and any slight lead results in it.
"but zed only beats karthus 60% of the time! see!, its not that bad!" - you have 4 other team mates/laners to worry about, not just the mid lane matchup and they have the power to influence what goes on in that mid lane. it wont just be 10-0 zed at your inhib with karthus 4 levels and 2 items down.