*how many languages would have given you [the luxury of programming effectively] for twenty years?
C++ doesn't qualify, to my mind, because the language has had many iterations and also because, as the post's author points out, writing C++ in the early 90s was not always a pleasant experience.
Python and even Perl are good contenders, as they have both been relatively stable languages. I'm not sure Java counts - Java 10 is quite different to Java 1.0, not just in terms of language features but often paradigms too (think 5's generics and 8's lambdas).
As for C# - I've never done .NET, so I'll have to take you on your word.
I know that Lisp has been largely stable, but are you sure it hasn't changed much? Programming paradigms advance, we didn't even have unit tests or continuous integration 20 years ago (at least not widely adopted in the industry). I find it hard to believe that even a Lisp programmer would be completely "static" across 20 years, i.e. the code written 20 years ago would be truly similar to the code he writes now.
So I'm not sure I buy this argument, unless someone has solid counter arguments.
I was paging through some old symbolics lisp machine code the other day and while I found some subtle differences in style, it was not so different from modern CL code. I think the differences that are to be found are less about the way one writes lisp and more that these days people make use of "standard" things like quicklisp, alexandria, fiveam, and other utility/portability libraries that didn't exist back then.
Edit:
I suppose a major change was that back then, CLOS was not yet part of the standard. There was a competing system being used at the time called flavors that had a lot of the same features. No one uses that anymore to my knowledge.
I think there was a big change in Common Lisp style in the late 2000s coming from Free Software, particularly concerning how macros and read macros were used. Edi Weitz's coding style had a big influence, and Tobias Rittweiler's named-readtables[1] was a paradigm shift. I think of Paul Graham's On Lisp[2] as the first wave of modern Lisp style, and Doug Hoyte's Let Over Lambda[3] as the second wave.
> I think of Paul Graham's On Lisp[2] as the first wave of modern Lisp style, and Doug Hoyte's Let Over Lambda[3] as the second wave.
Both are seen slightly controversial by some. On Lisp for example indicates that PG actually wanted to program in a different language - and eventually did: Arc.
I suppose I was thinking in terms of the OP's timeline - 1980-2000. I imagine the practice of writing Scheme code has changed a lot. Not to mention the number of teams migrating to Clojure.
C++ doesn't qualify, to my mind, because the language has had many iterations and also because, as the post's author points out, writing C++ in the early 90s was not always a pleasant experience.
Python and even Perl are good contenders, as they have both been relatively stable languages. I'm not sure Java counts - Java 10 is quite different to Java 1.0, not just in terms of language features but often paradigms too (think 5's generics and 8's lambdas).
As for C# - I've never done .NET, so I'll have to take you on your word.