We can't even, with foreseeable technology, go close to the speed of light. To propel a spacecraft the size of a small airliner at only one-tenth the speed of light requires as much energy as the US now produces in more than a hundred years. To go two-tenths the speed of light, would require 400 years of energy production. To go four-tenths the speed of light, would require 1,600 years of energy production. Each time you double the speed you quadruple the energy requirement. As you approach the speed of light, the energy required approaches infinity.
In Newtonian physics, this is because kinetic energy increases as the square of the velocity per this formula:
And at one-tenth the speed of light, it would require 44 years (about) to reach the nearest star (although for people on the ship would the time would 43.78 years due to time dilation caused by relativity). That is the Alpha Centauri star system. And there's no reason to think there are inhabitable planets in that star system nor alien life.
This is a conundrum for science fiction writers such as myself. In order to have our heroes and heroines have adventures on other planets and in other star systems, we need faster than light (FTL) travel.
In my novel Rock Killer, there is no FTL and the entire novel takes place in our solar system.
In my novel Forces, the humans don't have FTL but the aliens (some of which are evil) do.
But in my Treasures of Space series (Treasure of the Black Hole, Treasure of the Pirate Planet, and Treasure of the Rogue Moon), there is FTL travel. So we meet lots of alien species, go to lots of planets, and have a lot of fun. I stole "hyperspace" from other authors (and Star Wars). But coming up with an original FTL system is hard. In Forces, the aliens move interdimensionally and can travel between star systems in a moment.
So science fiction writers need FTL. Or they will be pretty much stuck in the solar system.
Larry Niven in his Known Space series of books and stories, had humans using slower than light bussard ram jets to colonize space. But it took a loooong time. (Then they were sold the secret to the "hypercore" by an alien species.)
But FTL is a mainstay of science fiction. And we're going to have to deal with that until and unless someone invents an FTL drive. Either that or you're stuck in the solar system or taking a long long time to get anywhere.