The reason language is infinite is that it's structured recursively. It's the same reason mathematical expression are infinite, because you can replace a number

The reason language is infinite is that it's structured recursively. It's the same reason mathematical expression are infinite, because you can replace a number with a bracketed expression. But computers can understand arbitrarily nested and large mathematical expressions given enough memory. So I think that it's misguided to argue that infinitude and recursiveness are the main obstacle to understanding natural language. The real issue most of the time is ambiguity and a lack of contextual knowledge, and in the general case, contextual knowledge requires general intelligence.