Let's be fair.... Poppy was not in the video Warriors because she has literally no reason at all to be there.
These video's are supposed to show canon or going to be canon lore. Stuff that actually happens or is going to happen in this world.
Now look at who made appearances... they all make some sense.
Caitlyn and Vi have been the ones capturing Urgot on his murder spree in the story "Child of Zaun". When now some Zaunite thugs are coming to Piltover, trying to free the dreadnought, it kinda makes sense that these 2 are there to stop them from freeing the criminal they caught themselves.
Ezreal is traveling Shurima quite alot to find ancient artefacts. He wants to become an archeologist, just like his parents, while trying to find them on his adventures. And guess who is also around in Shurima? Kai'Sa. When he suddenly opens a gate to the void (again!) in Shurima, while Kai'Sa is nearby noticing that, then she would obviously come to purge the voidlings. Because this is her entire mission.
We got the story that Sylas is going to the Freljord looking for allies for his revolution. Seems that this place is either in the Freljord or very close to it's borders, since it seems to be fairly cold and the barbarians that Sylas is leading into battle seem to be Freljordians. Lux and Garen opposed Sylas from the very beginning, Lux is actually the very reason that Sylas is free. Galio is literally the emergency call for Demacia when it comes to fighting mages and if I am correct, then Lux' magic also awakened him. It even is reflected that he jumps to emergency in the game with his ult.
Now look at Poppy. She is a girl wandering around trying to find the true hero of Demacia. This is her mission. I wouldn't think that she is going to abandon that mission to go to the Freljord to help against a revolt that is forming there. If she had appeared in that cinematic, then it wouldn't have felt all that natural for me. She would just be thrown in because.... why not?
Because that's all what yordles are to Riot: A fucking joke. Yordles can't be cool. Yordles can never be the central piece of a cool video.
About this part, I think the big problem here is actually that the yordles who live in other regions are not really important to the major plot....
Like, we have these stories about revolutions in Demacia and Zaun, Noxus invading other lands, Shurima trying to get back to it's former glory.
And then you look at the yordles of the other regions and notice... their stories are not really intertwined with these major plots.
Is wandering around in Demacia trying to find the true hero. Basically on her own little journey, we don't even know if she is aware of Sylas' revolution.
He is basically just a prankster in Bilgewater, hasn't been shown to care about the battle for power there at all.
He is Noxian, but he actually doesn't even Noxians his own people. He just fights for himself and would fight other Noxians as well. Dude's crazy.
Has his little inventions shop in Piltover, not involved in anything that goes on there politically or anything.
Basically same as Heimerdinger, just is down there in Zaun creating hexplosives and blowing up stuff here and there. Don't think he would intervent in any form to the whole thing going on with Urgot.
Sad mummy who literally obliterates anyone who gets close to him. Not involved in anything, being lonely is his shtick.
This guy is the only yordle outside of Bandle City involved in any major plot... hence why he has been part of the Awaken video. He is a member of the kinkou order. He has been equally as relevant as Akali, I think the video has shown this, too. But Irelia still got to be the major focus because.... again, leading the battle against Noxus is her whole shtick! The kinkou order doesn't even fight the Noxian's primarily, they are there to keep the balance between the spirit world and the physical realm. They just appeared out of emergency, like Galio in this new video.
Then we have the Bandle City yordles.... but Bandle City doesn't have any plot to this point, really. It is a mysterious place.
So it is kinda hard to put any yordles as a centerpiece of these narratives.... if they either are not involved in these stories going on at all or are just involved tangentially.