What he's trying to say is that no set of instructions can be written perfectly. Everyone has FSX installed in a different place, different OSs, different issues. Anyone installing freeware downloads has to be aware of these things - after all, you are getting something for nothing, so don't complain if the quality isn't quite professional.
Self extracting folders are not easy to do, both because of the path issue and also because a proper self extracting folder or installer requires buying often expensive programs to make them.
I fly through the valley of death, but I fear no evil,for I am at 80,000 feet and climbing. Let's powerdive and scare that poor soul in that Ultralight there.