The reason why a lot of seemingly simple balance changes don't get made.
It's because a lot of the unhealthy mechanics are all tied together in a tangled knot. If you were to get rid of one, you would end up finding a whole new problem, and because riot only makes a move on the knot once every two weeks, either they would need to fix the whole mess in one patch or they would need to essentially render the game unplayable until they solve the whole issue, which could take longer than a full patch with all of the misc things that can only exist in an inherently unfair environment.
So riot has chosen to just ignore the problems entirely, atleast for the time being.