You're telling me that maybe we could terraform an entire planet in 300 years

That's insane, we would have to create a magnetosphere, create and pressurize an atmosphere, somehow deal with the fact that Mars has less than half of Earth's gravity, the reoccurring dust storms that would block out the sun a week at a time, and the fact that Mars' average temperature is the same as Antartica's. We have theories of how we could do this but they require a stupid amount of energy. We can't even solve the energy crisis here and we're going to have enough to pack up and remodel another planet?