I've headcanoned it that Discovery was covertly part of a Section 31 collaboration with the Department of Temporal Investigations to test technologies and materials acquired or implied through various temporal incursions, the goal being to see which ones could be arrived at and used without causing potential disturbance to the timeline. The updated look of Federation ships is also a result of that, producing a 23rd century which looks quite different but in which events play out functionally the same.