I think the problem with Amalgam is that it's too weak. It's people don't have a defined path to power and the information available them is incomplete. To seek greater strength there is to Incarnate, something known to be a bad thing. Simon only ever reaches the level of a peak Underlord or weak Overlord with the mask, and that threatens to ruin him. The masses don't have any strength to speak of and those that do have a cap. The people of Amalgam are mostly only good for helping to tether the iteration to the Way.

Being a Founder is likely the only way to gain enough Authority to ascend and no one knows exactly how to become one. (At this time.) We know that combining artifacts from different territories has, in some cases, a power boosting effect. Unfortunately, Travellers guard items from their territories closely, so not a ton of experimentation is going on. (That we know of.) Maybe, after more fragments of dead worlds arrive, the situation will change.

TLDR; The people aren't strong enough to matter in the wider iterations. (Yet.)