The problem isn’t travel time, it’s speed. Space itself is continuing to expand, at a faster and faster rate. It’s expanding so fast that we’ll actually never reach far out with conventional means. We’d just endlessly drift through the darkness because we wouldn’t be able to go fast enough to reach anything. A generation ship would simply not be able to get anywhere, ever.

I mean, maybe we can make it into another very close system, but what are the chances that there’s anything even close to being habitable?