Lambda calculus is the basis for many old and new languages alike, and there are a plethora of…
W. Brian Gourlie

I think what the author meant was that in terms of how typical professional programmers interact and reason about their code, the larger community is still pre-scientific. Though Haskell and other lambda-calculus-based languages, not to mention numerous other academic insights, have proven quite useful in the understanding and reliable creation of code, I don’t think many people would say they’ve become very prevalent in the industry as a whole — they’re still confined, largely, to academic projects and the rare senior-dev idealist. To a significant extent, it seems to me, many of the people driving the culture of programming are still often driven by opinion and partisanship, rather than careful consideration of the problem space of their field — that’s what I think is meant here by “pre-scientific”.