> I wish I better understood how ingesting and averaging large amounts of text produced such a success in building syntactically-valid clauses and such a failure in building semantically-sensible ones. These LLM sentences are junk food, high in caloric word count and devoid of the nutrition of meaning.

I suspect that's because human language is selected for meaningful phrases due to being part of a process that's related to predicting future states of the world. Though it might be interesting to compare domains of thought with less precision to those like engineering where making accurate predictions is necessary.