“Just because we haven’t figured out faster-than-light propulsion technology, doesn’t mean others haven’t.”
Except it’s not that “we haven’t figured it out”, it’s that we have figured out it’s basically physically impossible.
Let’s review the possible ways one could travel faster-than-light and why they don’t work:
1 - Acceleration (conventional rockets, etc): Doesn’t work because you can never accelerate a mass to light speed, much less above it.
2 - Wormholes : We don’t even know that they can exist, and if they did, they would take more energy than we can generate to create them, and even if we could create one, we could not traverse them and survive.
3 - Warp drive : Requires creating a zone of negative energy density, which doesn’t seem to actually be possible in this universe.
So that pretty much covers all the bases. Don’t hold your breath hoping for FTL travel, either by humans or aliens.
"Heavier than air travel is impossible!"
Thus spake the leading scientists and wizened thinkers of the late 19th century. The Wright brothers ignored them and kept on working toward their goal of mechanized flight.
If there's one thing history teaches, it's that every generation believes it has reached the pinnacle of all knowledge in the sciences - and that every generation has been proven wrong.
We're no different than prior generations, and will see our scientific canons and fixed rules fall by the way, in time.