Then we know all there is to know about our four dimensional space-time we live in, right?
There is nothing left to figure out, right?
We know everything about that geometry, right?
There are no unexplained anomalies in that geometry, right?
We don't know "everything" about even very basic things like energy, momentum, and of course, space-time. That doesn't mean these things can have arbitrary properties yet to be discovered, and it doesn't mean we know nothing.
One thing we know about this space-time is that the quantum numbers associated with material representations (mass, energy) if propagated faster than light must produce causality violations. Were this not so -- just for one singular but highly important example -- Maxwell's equations could not hold.
Now, you may doubt the consequences of arcane and still speculative areas in which we really can't achieve the energies we need for experimental verification, like cosmology or particle physics. But the universe is doing literally billions of little experiments with Maxwell's equations within the space of a few angstroms every nanosecond. And guess what? It's never found the electromagnetic field to be anything but Lorentz Invariant.
If you aren't convinced by that, and aren't convinced by the fact that macroscopic experiments involving electromagnetic fields show that all observers see the electromagnetic stress tensor in a way that obeys the special theory of relativity, I really don't know what else to tell you.
We live in the universe we live in, not in exciting, wonderful, but physically nonsensical universe of Gene Roddenberry.
We don't know everything about energy, but no one seriously believes that we're going to invent a Perpetual Motion Machine of the First Kind. Same for entropy, but again, you will find no serious scientist or engineer who will take up your challenge to create a Perpetual Motion Machine of The Second Kind. Our basic understanding of momentum could be improved. Does any physicist think we will discover that the Uncertainty Principle doesn't apply somewhere?
No.
"There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy."
- Hamlet (1:5.166-167)
True and inarguable. But there are some things that are not in heaven and earth, and pretending won't put them there. I cannot profess to have even the most infinitesimal understanding of God's mind. But I know that he is not evil. And I know that superluminal travel is not possible.