I'm not aware of genetic algorithms being used in GenAI. Genetic algorithms really had their hayday in the 1990s to my understanding. They're generally very limited due to the heuristic like approach to refining the underlying model.

As for structured vs unstructured, you can typically think of it as whether or not the information is "machine readable" or has an explicit structure.

With the Factorio setting the structure is the grid (how many spaces are there to work with) and what structures you can place on each grid space. So in an x by y rectangle the algorithm has to decide what of the z types of structures should be at each spot on the grid (effectively an xyz output space)

Conversley with language/text you run into many different problems. Just trying to define how many words there are is an ever evolving challenge. While you might be limited to 26 characters, there are no rules about how long or short a sentence is, grammer is flexible, conjugations are all over the place, and the meaning of a sentence can change based on the last word Garden path sentence. Essentially, there is no definitive meaning of any sentence without a contextual lens to provide it structure.