Riot is great at making beautiful cinematics, but the lack of battle composition experience and biased toward cooler/newer/sexier champions makes things a little weird when they also try to pace something to a song. It doesn't even take much to fix either problem.
Garen knocking Sylas back a few steps in their first clash would imply momentum and power behind his attack. Sylas has some kind of lore defense against Garen's sword, sure...but Garen easily weighs 300 pounds and he basically landed on Sylas sword first. Having Sylas stumble a little would a nice.
Ezreal was a mess. Assuming this isn't his first time using his magical gauntlet, he should E toward the exit and then fire Qs at the voidlings as he runs so he can get his E up again. Or he could try attacking the door itself; if Kaisa could destroy it why can't he? Why not put the priceless artefact into a pocket on his belt or tuck it into his shirt? Was he planning on carrying it in his hands until he got home?
Kaisa diving into the Voidlings made no sense since she didn't bother to use any melee attacks. HAVE HER PUNCH AND KICK if she's going to charge into melee. There is no reason to hyperspeed dash from a safe marksman position into danger so she can do catwoman backflips and...continue using ranged attacks at pointblank range. For the sake of the video having her refuse to give up on defending the exit and getting dogpiled as she tries to stop the voidlings from getting out would have made more sense. Or they could have used some kind of visible portal that needs to be disabled, forcing her to wade into the enemies to try to reach it.
https://www.sakugabooru.com/post/show/15509
^Example of a ranged attacker entering melee for an instory reason that's evident without reading 50 backstory novels and 2 lore-bibles: The injured gunman realizes he can't aim anymore so he moves closer, wagering that he would get one good shot off on the swordsman before the swordsman could kill him. We can see every part of that process. He takes aim, can't hold his target, then moves forward while still trying to shoot. Kaisa, on the other hand, apparently wants to _style _ on her enemies.
Lux was AFK in the frontline for 3 scenes. 3 Scenes of just cowering as allies trip over her while trying to save her. The feminists will be outraged.
Vi and Cait did well until Cait stopped attacking Urgot to Vi could get the kill; she could have tapped his other leg, or tried for a body shot, or tried for a headshot, or popped a few more tubes, or SOMETHING. Ezreal and Kaisa are able to precision-shoot around allies, but Cait, the sniper who did this moments earlier, cannot? Vi Slow Motion Pimp-slapping some nameless minion before grabbing Cait's gun was a waste of time since that could have be devoted to the champions fighting.
Vi melee attacks-> Gun grab->Gun toss-> Cait peels minions off VI->Perspective swap to Urgot towering over the battlefield and charging at them-> Cait shoots Urgots leg-> Vi finishes dodges minions and uppercuts the injured Urgot-> Cait finishes last minion behind Vi.
Simple. Plenty of the same stuff in that, but we also get the implication of trust and focus on the other's safety ("Cait needs her gun NOW!" followed by "Cait is a a goodmode marksman. She can shoot around me. I need to keep fighting." followed by "Alright, I need to focus on this dude. Cait has my back." on Vi's side, and "I'm back in action. Gotta keep Vi safe." followed by "Big enemy. Oneshot? Can't. Bring it down to our level, then keep the losers from dogpiling VI.") all in a few split seconds. We see an unoptimized version of this.
Galio Ulti sucked. Sylas stood a few feet away and backed up on his own, the freljord barbarians fighting on the frontline stumbled backwards slightly, and either Galio healed every demacian soldier (while repairing their armor) or he brought a squad with him to assist; not a single demacian was injured or had damaged armor or showed the slightest hint of fatigue. Those dudes joined the battlefield like they had just finished their pre-workout stretches; nary a stumble in sight which is odd considering that they either rode a massive gargoyle into battle just now OR they were fighting for their lives for the last 10 minutes. No one got knocked up by Galio's ulti. We KNOW Riot is fine with people getting tossed into the air by an impact too, since Garen and a few Demacian soldiers were sent flying by the boulder that destroyed the fort's gate; did they just run out of budget at the end?