Not all champions exist at the same moment

Well let’s see how far this rabbit hole goes to what does exist at the same time.

Taliyah was part of the Noxus invasion of Ionia, met Yasuo and now is dealing with Xerath. Ok so that’s basically the entire Noxus side, Ionia side, and Shurima side co-existing. Through Noxus we get Urgot which hasn’t yet interacted with anyone in Zaun but we’ll see how that shakes out. And from Ionia we then get the rest of the Darkin. But wait Sivir interacts with Cassiopeia who’s sisters with Kat who Jaredan has said is still going to have a funky relationship with Garen. Ok, that puts all of Demacia on that timeline. And since Taric is Garen’s friend and then gets sent to Targon where he becomes an Aspect and adding Targon to that timeline. Which means we get to add Nami because she’s following Diana.

But wait, Gangplank’s lore still references Swain. So that’s Bilgewater in the works too, and from that we get TF, Graves, and whoever they’re going to interact with from then on. That also puts Hecarim, Thresh, Lucian, and Olaf present.

So going back to the Darkin, that means Aatrox is present so from there we get Tryndamere which leads to Ashe and by extension the Three Queens and all of their minions.

So who isn’t accounted for? Piltover and Zaun are still separate right up until Urgot talks to anyone. Most of the yordles but they’re timeless or something. Bard. Nautilus. The Freljordian demigods and Braum. The demons that aren’t Nocturne. Technically Vayne and Eve are simultaneous but I don’t know for certain if either of their lores reference anything that can date them to the same time as the rest of Demacia.

Dont change his words, He said: "It's not even entirely clear whether all the LoL champions exist at the same time in the lore"

Sure, its possible that not all champs exist at the same period of time, but not confirmed.

Stachlocke said they are exploring the idea, he didn't confirm this. If summoners are to return to the lore this is key to their implementation as the "League of Legends" would just be recollection of heroes during Runeterra's history. I have thought of this a while back, if it were to go this route then I see an adult Annie becoming the 'narrator', telling stories of Legends that walked Runeterra when she was younger.

All of the characters seem perfectly present in the present. Oh sure some existed way before others, but as it is, they are all present and alive (-ish if you could Shadow Isles peeps as alive) at the same time.