"We want Less Mechanical Burden"
So I see Alistar gets a nice buff to make his combo easier. Don't disagree with that at all, since it's pretty much standard to play Alistar well.

So when can we expect those Riven changes?
So I see Alistar gets a nice buff to make his combo easier. Don't disagree with that at all, since it's pretty much standard to play Alistar well.

So when can we expect those Riven changes?
Apples and oranges, Alistar's punishment for messing up a combo is much, much more severe.
They are the same in that it was a mechanical meta-game of knowing specific, quirky execution techniques that don't really have much to do with what is intended to be skillfull play in League
Intended or not almost any champion involves animation management of some sort. Problem is when a newbie who would want to learn Alistar needs to spend hour or a few practicing this combo in customs before he stops hurting his team.
Do people really find animation canceling hard?
Oh Jesus lol
There's a difference between the two. Alistar is getting this change because they want the difference between regular play Alistar and competitive play Alistar to be less extreme - they make it easier for normal people to play him in exchange for making him less rewarding when played to his best. This will make it easier to balance him.
Riven's animation cancelling is similar to his mechanic but unlike with Alistar, it hasn't created a huge gap between pro play Riven and regular play Riven, so it doesn't need to be addressed.
Also, nobody with a clue want Riven to be made easier to play.