A lot of GNU software has some other FOSS equivalent that it can be replaced with. GCC, however, was basically the only production-worthy FOSS C/C++ compiler for a long time, until Clang came along.
GNU was the very first free Unix reimplementation project. Without it, maybe only excessively expensive commercial Unix systems would be available alongside Windows. Although 386BSD was also an early effort, the intense FUD campaign prevented it from being used for more serious purposes. At the time, GNU/Linux played a crucial role in competing against commercial Unix systems.
A lot of GNU software has some other FOSS equivalent that it can be replaced with. GCC, however, was basically the only production-worthy FOSS C/C++ compiler for a long time, until Clang came along.
GNU was the very first free Unix reimplementation project. Without it, maybe only excessively expensive commercial Unix systems would be available alongside Windows. Although 386BSD was also an early effort, the intense FUD campaign prevented it from being used for more serious purposes. At the time, GNU/Linux played a crucial role in competing against commercial Unix systems.