Time. We still don't think about time properly - there are likely some huge technological gains if we can unlock time in relation to physics (not in terms of sci fi time traveling).
This isn't entirely accurate. We will not be able to visit the vast majority of the universe even given infinite time if we are not able to travel faster than light. Like 94% of the universe is unreachable without FTL, even without time constraints.
I've never actually looked up what the "quadrants" are in Star Trek. Apparently just our one galaxy divided into four. 6% of the universe is indeed an unfathomably large amount of space.
