For a while now, Riot has been talking about clarity and windows of opportunity to trade in-lane. This clarity ranges from circles in abilities/items, like Ornn's E/Redemption, to rectangles and other markers such as Kayn's W and Ivern's Daisy knock-up. Additionally, Riot has been known to ADD clarity to a champions kit, such as after Zed came out and the X was added so players would know who he was ulting.

So it baffles me when animation cancelling still exists on a number of champions considering it goes against the Riot mantra. The biggest offender is naturally Riven, though others like Renekton definitely abuse this too.

The new Janna PBE changes explicitly mention how the CD on her shield is changing to allow better opportunities to trade in lane. Trading in lane being the important part- how can we effectively trade with a Riven in lane if we're not sure what spells she still even has up? In the same thought, how are we supposed to know which spells are up if we can't see them being cast, since they're being cancelled?

Furthermore, Riven is considered a Skirmisher by Riot's own definition- "...Skirmishers aim to shred through any nearby enemy that approaches. Because Skirmishers lack high-end burst damage or reliable ways of closing in on high-priority targets, they are instead armed with situationally powerful defensive tools to survive in the fray, along with extreme sustained damage to cut down even the most durable targets." Animation cancelling allows Riven to not only have reliable options of closing in, since she's moving so fast, but it allows her high-end burst damage. This definition likens Riven more to an Assassin or a Diver than a Skirmisher.

Either way, it's clear that animation cancelling is a point of contention- look at Nidalee and Graves. Both had their animation cancels taken away.

Tl;dr- Riot needs to take a stance on animation cancelling for clarity and to allow better trading in lane. Should it be allowed, it needs to be brought back to champions that previously had it.