My understanding of the reason FTL travel is impossible even if (huge if because it requires infinite energy to start and stop) we could somehow figure out the boundaries, is that it breaks causality. Causality travels at the speed of information and to my understanding that is at c. If you launch a ship in response to a signal, and the ship goes faster than light, you have the potential for tge ship to arrive before the signal summoning it is sent. And this assumes that all the negative energy and negative mass and space debris problems are actually surmountable by beings anywhere in the universe. If you’re talking about breaking causality, either we admit that we know literally nothing about anything in physics, or we admit that we’re likely talking about a fantasy and we’d get equal results by spending billions to try and mix Floo powder and travel across Europe by fireplace. As for wormhole theory, I’m not sure it actually fairs much better, unless we’re going to start dosing up pilots with worm-puke gas until they turn into fish-like superhumans who can predict the future.
If you really get into the ins and outs of theoretical physics down there where the "Theoretical" has a capital T and the "physics" is in italics, you start tripping over weirder shit: - Quantum entanglement is instantaneous and what keeps it from transmitting communication is the observer effect - The observer effect is some hand-wavey shit along the same lines as wave particle duality, IE "shit that was made up so that undergrads could move on" - The theory of relativity says you can't accelerate something TO the speed of light. It also says you can't decelerate something FROM the speed of light. Which means that anything going faster than the speed of light can't be made to go slower and anything going slower than the speed of light can't be made to go faster which means they can never interact. It does NOT forbid either from existing. The speed of light is just where the asymptote lives. There are asymptotes throughout mathematics. One can, with confidence, say that there are iron-clad laws preventing information or matter from traveling past the speed of light. One cannot, however, point at theoretical physics and say "because all this shit is absolutely rock-solid." Edwin Hubble turned the Andromeda Nebula into the Andromeda Galaxy barely 100 years ago. Superconductivity was discovered in 1911, but superconductors you could wow your physics class with showed up in VWR Scientific when I was in high school. The age of the universe has gained two decimal points of precision since I started college. Not saying warp drive is right around the corner, saying that "faster than light travel appears to be impossible" is likely a safer thing to say than "faster than light travel is impossible" based simply on scientific progress.