I don't know if a generational ship is absolutely required. There's this assumption that interstellar ships would be full of human astronauts who are alive and awake. But that might not be strictly required. You might be able to have everybody go there frozen. Or have a robot ship that gives birth to the colonists from an artificial womb on arrival.

> You might be able to have everybody go there frozen.

Common trope in sci-fi, pretty much impossible in practise. Humans aren't capable of surviving being frozen, we lack the genetic machinery for that. Could you breed/engineer hybernation-capable humans? Sure. Otherwise this approach would require to literally being able to kill and then resurrect people at will.

> Or have a robot ship that gives birth to the colonists from an artificial womb on arrival.

I like this idea. It kills two birds with one stone: for one, fertilized eggs and fetuses can be stored safely for a long time.

Secondly - and I think this is something that's underdiscussed - genetic modification will be necessary anyway. The target environment won't be a carbon copy of Earth. Different atmosphere, different gravity, different starlight, different pathogens, etc. If you insist on colonising planets and start terraforming via automated means ahead of time, the resulting ecosphere will still differ from Earth and adjustments will be necessary. A ship carrying unborn settlers would be informed of the specifics of the target world and the ship's biolabs could make genetic alterations accordingly.