I don't understand how you can say that TOS wasn't set up to create a larger universe when that's exactly what it did. All of the Trek spinoffs are still using the basic framework that TOS established. Some of the shows have expanded greatly upon that framework, yes, but all Trek shows are still using elements like a united Earth, Vulcans, Klingons, Romulans, Orions, Andorians, Starfleet, the UFP, warp speed, the transporter, phasers, photon torpedoes, etc.