Even if it's possible, interstellar colonization could simply be too expensive and offer too little benefit.
There are large areas on Earth we haven't colonized and seem in no hurry to start: deserts, poles, sea floor, etc.. The expense and technological challenge of doing so are orders of magnitude less than delivering a large enough quantity of people (hundreds of thousands? millions?) to start a technological civilization with no reasonable lifeline from Earth.
It's probably cheaper right now to protect our planet from catastrophic events (e.g. asteroid strikes) than the best case scenario: to colonize a perfectly earthlike planet with edible biota orbiting Alpha Centauri.
There are large areas on Earth we haven't colonized and seem in no hurry to start: deserts, poles, sea floor, etc.. The expense and technological challenge of doing so are orders of magnitude less than delivering a large enough quantity of people (hundreds of thousands? millions?) to start a technological civilization with no reasonable lifeline from Earth.
It's probably cheaper right now to protect our planet from catastrophic events (e.g. asteroid strikes) than the best case scenario: to colonize a perfectly earthlike planet with edible biota orbiting Alpha Centauri.