There is a thesis held by some in the science community and it goes like this:
Our galaxy has so many worlds and has existed so long, that everything that can happen has happened, out there somewhere. You name
it and some alien civilization has done
it-- provided it is physically possible.
If warp drive were possible, it would have been invented billions of years ago by an alien civilization in our galaxy.
They would then have built a galactic empire and at some point, long before man evolved, they would have found Earth and colonized it themselves. Their expanding population needs real estate and other resources.
In that case, their animal control department, or maybe even terraforming efforts, would have prevented our evolution.
Since we are here, and there is no credible evidence that space aliens ever were, it follows that warp drive is physically impossible.
Are we all agreed?
To go all vulcan on you, I find your logic flawed.
1.>The universe is not limited to our Galaxy.
2.>Our solar system might not have even formed if some ancient civilisation discovered warp drive.
3.>Any FTL drive system might be limited to only a few hundred times the speed of light.
4.>They might have some sort of directive to stay away from less technoligcal advanced planets.
5.>Who knows if some alien civilisation didn't kickstart the creation of life on Earth (improbable yes.)
6.>Perhaps this alien civilisation destroyed itself before they reached Earth.
7.>Earth might not suit their biological requirments.
I could go.