It's just not that simple to build userspace binaries that use lots of libraries

True, and pkg-config has come a long way lately with things like variable support and even msvc syntax handling. It doesn't help very much if you need to test for build options, though there's no reason why it *can't*. pkg-config's --variable feature would let you do build option tests ... but far too many packages fail to set appropriate .pc variables for important build options.

At least pkg-config makes version tests, cflags discovery, etc a whole lot easier.