You were almost coherent until you get to your assumptions about 'what people would have me believe' about linguistic universals. There are many universals that can be explained by generative grammar. There are numerous examples. 'tradeoffs between different needs' is not an actual argument. It is ridiculous that you are replacing 50 years of work with something so unscientific and vague.
I think you know damn well that there are patterns in the mind. They are posited for many things. Generative Linguists want to determine which of those patterns can account for certain linguistic phenomenon.
Physicists and Mathematicians study idealistic events, matter and object in idealistic spaces and conditions all the time. They don't study unicorns.
You cannot account for the fact that humans can instantly parse novel sentences using 'complex and messy social conventions'.
I cant tell you have no idea what Generative Linguists do and have never really read any of the literature. You (like a lot of people here) are just repeating the predictable things people say when Chomsky comes up that they probably overheard once.