Man would never travel beyond his interstellar neighborhood in his lifetime. He can, but he'll never return home in the lifetime of everyone he knows. If he travels further, he will return to find even his home is long gone. This is due to one vicious supervillain ruling our universe. A supervillain named "c". "c" is a velocity, a velocity impossible to surpass. What's even more cruel about this supervillain is that it will outsmart you no matter how you wanna outsmart it. Yes, all methods of FTL can and will lead to causality violations, and there's no way around it. However, this villain is also the backbone of why everything in this universe behaves as it does. Unless...
This supervillain c will make interesting sci-fi plots such as galactic empires completely impossible. You can't keep an empire united when even a simple "execute political dissidents" message takes multiple hundreds of lifetimes to reach the "rural" areas of said empire. So i propose a Newtonian universe where the speed of light and other massless propagation is infinite. I know this would cause Olber's paradox of infinitely bright sky but we can solve that by saying this universe is not infinite, and non homogenous at all scales. However, this universe is huge. 21st century humans might as well think it's infinite. The furthest galaxy as of 2022, called HD1, lies 13.5 billion light-years away in light travel time. The luminosity distance, i.e. the distance based on the observed brightness of the galaxy alone, if it wast't subject to cosmological redshift, is 650 billion light-years. This is thus the distance humans with 21st century technology can observe, the actual universe is much larger.
As the speed of light is infinite, the concept of "light-year" might as well not exist. Instead, I'll imagine people using parsecs instead when referring to interstellar distances. 1 parsec is approximately 31 trillion kilometers or 19.3 trillion miles.
Now this is all settled, the supervillain c is gone. You can travel however fast you want. There won't be black holes anymore though, but an infinitely dense singularity tearing apart everything that comes near it is still possible, so quasars can still be a possibility. Only difference is that it's theoretically possible to escape it no matter how close you get. And also, no time dilation, the whole universe shares one universal time.
Wait, didn't i say this supervillain c is also the backbone of why everything in this universe behaves as it does? Now that it's gone, what adjustments to physics do I need to make in this universe in order to have it behave the same as this one macroscopically? As in, if I get teleported there right now, I won't detect any difference except that the speed of light is infinite. Every physical, chemical and biological experiment I do there yields the same results as if I'm doing it here, except the ones related to relativistic velocities. Do i need to rewrite all the fundameltals in the universe in order for my idea to work?