I would still hold off the "braindead" part of the description though, simple champions rely more on macromanagement to win games compared to the flashy "outplay" champs who waltz out of bad decisions just because they happen to have quick fingers.
It's not "E first, then land 1 autoattack, reset it with Q, followed by whatever item, then R to follow up, then disengage with W.. ", but more of "The top has gone roaming, then I will take the top turret, he's back so I'll have to back off for now but I can probably steal his red since his jungler is ganking mid... or I could TP bot for a gank and get dragon... etc etc...
They're different kind of skills, and some champs just require more micro than others, but as a result, they get to "outplay" certain situations that would've been really unfavourable for the simple champs, meaning they don't really need as much macro.