It was declaring that the developer was incompetent. That's needlessly insulting to anyone. Making a mistake doesn't make you an incompetent person.
#if defined(__GNUC__) && defined(__GNUC_PATCHLEVEL__) && \
(((__GNUC__ == 9) && (__GNUC_MINOR__ <= 3) || \
(__GNUC__ > 9)))
Also their arrogant attitude. Incompetence is rarely the only problem, it only gets problematic if paired with disfunctional management or arrogance.