Just a thought for an alternate setting, set primarily on future-Earth an arbitrary number of centuries after the Singularity or something like it. Instead of being interstellar entities spread over chunks of the universe, the Civilizations arefor the most part"national" territories on Earth itself (and layered over the evolved/mutated remnants of still-recognizable real-world cultures/countries). This would be an future in which the major (and managed) "ideological" tensions are between different but continually viable modes of physical existence.
So, say, the Daoine might be centered around what used to be Ireland, now vastly transformed; the Disciples congregate in one or more artificially-isolated areas with artificially-cleared night skies; the Stardwellers actually do go starfaring but have a primary "homespace" in cislunar orbit; the Independents are primarily O'Neill colonists, also cislunar, with colony cylinders in the thousands; the Old-Worlders and Cargo Cultists live in preserves set up in the interstices between the various posthuman enclaves — all of which are bound by some sort of worldwide compact (and technological enforcement) that prevents them from physically encroaching upon one another; etc.
There could even still be wormholes — their range is just more limited: instead of being interstellar, they're mostly only workable out to about the farthest extent of this Earth's Civilizations, so worldwide/cislunar; while to reach whatever few solar or extrasolar colonies there may actually be, you have to transmit yourself, at lightspeed and at cost, however defined.
Plots come, I guess, precisely from the tensions of all these fantastically powerful civilizations pressed up against each other and still trying to share a world. Kinda like now.
