The "Mortal Reminder" Video Failed
With the K/DA single skyrocketing to over a million more views in just four days than Mortal Reminder has in over a year, I want to address some of the mistakes of that video that have been done better in the K/DA one.
First and foremost, the song picked wasn't the right choice. My personal opinion is that Bloodthirster and Infinity Edge were the best on the album, but they wouldn't have been the right either. Why? Because "Kayle" isn't singing in any of them. And the video, above all things, was supposed to boost the sales of the new Pentakill Kayle skin. But they decided to have her appear at the end during a song she has no part in rather than have her appear at the beginning to sing either the duet Frozen Heart or her solo Tear of the Goddess. If either of those songs had been chosen instead, they could have shown the skin on screen for most of the duration, prompting people to buy it.
And second, the visual style is plain ugly at parts. Particularly any time a yordle is on screen. The way the hair and fur was handled was terrible, and that's inexcusable when Karthus's hair in that same video had no issue. If it were done in a style more true to the game, or even just less photo-realistic, it'd have been fine.
The K/DA video fixed both those problems easily. The skins are present in the video because they're a new line. Easy enough. And the visual style is just... more polished. I'm not saying the style of the Mortal Reminder video was bad, but it lent itself to inherent problems that don't exist for the style chosen with this one.
It wouldn't surprise me if Riot went with this style of animation even for lore related clips going forward, because while it looks less realistic it also looks much more like the actual game. And seems much less laborious to animate.