Earlier quoted context omitted.
> but writing a makefile and only evaluating against it makes it difficult to guarantee that you will see the same behaviour on a non-GNU system This would only be true if the entirety of thr GNU suite were necessary for GNU make to work. But it's not, so I always find this kind of argument really weird. I mean it's not necessarily completely irrelevant criticism, but I somehow only see this level of criticism aimed…
You are being overly defensive here. What I wrote had nothing to do with GNU in particular, as I hope I made clear in the very next sentence after the one you cited by stating that the same is true for BSD make implementations and portability. The parent asked about GNU make, thus I logically kept on talking about GNU make.
I misinterpreted the whole thread as "what's wrong with writing makefiles for GNU make specifically".
Which is subtly a different question (and to which the answer of course is "nothing, as long as you're happy to specifically use GNU make to run them").