That's a myth. Actually there are lots of project with domain specific languages and in the case of Lisp they are often directly embedded. Having OO- or functio

That's a myth. Actually there are lots of project with domain specific languages and in the case of Lisp they are often directly embedded. Having OO- or functional interfaces to learn is not much different from learning macros. USING the macros is not a problem. MAINTAINING them might be a problem, because new people might have a hard time understanding to work with a language which has meta-level programming directly integrated. There are more languages which now are adding some kind of macro facility (example Rust), so there might be now more programmers getting familiar with meta-level programming with macros. Projects like planners for public transport use special language extensions and if they have a market, they go for a long time. Other example, a specialized CAD system will have its own language extension for expressing generative CAD operations. Sometimes there are projects which are replaced with different technology. For example a web store generator. But there the domain technology typically changes that some of these sites have three technology transitions in a few years. Every project owner has new tool preferences, influenced by the market. It might look like that old code is not understood, but the problem is actually that the code is no longer fashionable. Writing enterprise applications is largely done by Java and not C++. The reason to replace an enterprise application with one written in a newer language (like Java) has many reasons: technology no longer seen as fashionable, fewer trained developers available, trained developers to expensive, age bias, new libraries not available for the older language, etc.