It was always a part of it though … travel times were always there and relevant, the delta quadrant was very far away, getting to the battle in time wasn’t always possible, being alone when in trouble was almost always the point … space hadn’t been reduced from a final frontier to an irrelevant playground.
a single ship having it
Well this was part of the contrivance … once Discovery made it work why wouldn’t the whole federation be running spore drives ASAP? Security wise they’d be nearly unstoppable.