I think I understand where RMS was coming from RE "recursive variables". As I wrote in my blog:

Recursive variables are quite powerful as they introduce a pinch of imperative programming into the otherwise totally declarative nature of a Makefile.

They extend the capabilities of Make quite substantially. But like any other powerful tool, one needs to use them sparsely and responsibly or end up w/ a complex and hard to debug Makefile.

In my experience, most of the times I can avoid using recursive variables and instead lay out the rules and prerequisites in a way that does the same. However, occasionally, I'd have to resort to them and I'm thankful that RMS didn't win and they exist in GNU Make today 😅 IMO purist solutions have a tendency to turn out impractical.