Take optimisation, another task like interpolation which the machine does to transform our program text into an executable

We'd like exhaustive optimisation, in fact that can't be done and today we're used to a relatively aggressive optimisation which would not have been possible fifty years ago, but we're nowhere close to optimal for non-trivial programs.

Or correctness, it seems as though global static analysis should be possible, at least for something modest like a typical Unix utility - nope, that is known to be mathematically impossible for even quite modest software, only local analysis is at least plausible and its effects are much more limited than we might hope.

I, too, struggled to understand the meaning of this sentence. I can parse it, I guess, but any meaning I try to guess for it is either implausible or irrelevant.