They don't cause a ripple effect because they are myths.
Azir caused a ripple affect because he dealt directly with other characters. Then there was Bard, Ekko, Tahm Kench, and now Kindred.
Ekko had impact onZaun because he grew up there. We understand that Zaun is inhabited by kids who aren't generally insane. There are memorials, so on and so forth. We even got some idea that not all of Piltover is bright since the "Whistling Man" was from Piltover probably doing some black market work in Zaun.
Then there's Bard, Tahm Kench, and Kindred. Why do they feel like they don't have a ripple effect?
They are the "mythos" of Runeterra. They are what caused Runeterra to be what it is, or, at the very least, helped stir some of the cultural phenomenon found within it.
For Bard, he is the reason there are people that work around the idea of pasing down stories from word of mouth. They identified and labeled themselves under his name, "Bard." They are bards. Stories of a Fallen Kingdom (Pre-SI), tales of Watchers and even the downfall and destruction of Shurima. They all had something to do with Bard. And if they didn't, the bards still believe, and it is one of the many tales they tell of the constellations, the STARS THEMSELVES.
Tahm Kench, an ancient Crossroads demon older than what any of us could imagine. So old, in fact that even his image was carved into the cultures of other places. Just like Aatrox, people made figures of him, busts, and carvings. This is a demon. A supposed boogeyman that embodies the very concept of gluttony and greed. What better thing than to inspire Bilgewater, a place where it is kill or be killed. A culture where you have to con the very man next to you just to have enough gold to buy yourself a loaf of bread. A place where if you were foolish enough to make a deal that's seemingly too good to be true, you will lose EVERYTHING.
Then there's Kindred. They are the concept of death themselves. No. Not the concept. They are death. And sure, Kindred may be at a battlefield, but death is prevalent everywhere. Kindred has the power of omnipresence. They can be anywhere at anytime in more places than one. Remember, this is a being who goes by different names in DIFFERENT cultures. Their very existance serves as the focal point, the inner workings of how life is wrenched from the body and disappears. Either through acceptance of one's end with the piercing shot of Lamb's arrow or by the losing battle of one fending themselves from the gnarled fangs of Wolf's hunger. The earliest stories and myths in our world revolves around death itself, and Kindred is the image and personification of that very myth. They are the grim reaper.
These three beings are the foundation constructs of what Runeterra is today. Through centuries and millenniums of influence, they cannot cause a ripple within the water, for they are the streams from which the water flows out of into the primordial pool of Valoran and the Legends of Runeterra.
**TLDR; ** They are influencing basises for the world cultures. The impact and ripple effect they had has occurred long before most of the other champions even appear within the Lore.
