All religions are man made.
It's usually invoked as a way to say that they're all necessarily fallible, involve personal human interest and bias, and are just as prone to corruption and falsehood as any other human institution.
I want to go on record that I believe that Catholicism is absolutely a man-made religion.
Of course, the man who made it was Jesus Christ Himself:
15 He said to them, "But who do you say that I am?" 16 Simon Peter replied, "You are the Christ, the Son of the living God." 17 And Jesus answered him, "Blessed are you, Simon Bar-Jona! For flesh and blood has not revealed this to you, but my Father who is in heaven. 18 And I tell you, you are Peter, and on this rock I will build my church, and the powers of death shall not prevail against it. 19 I will give you the keys of the kingdom of heaven, and whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven."
Of course, that doesn't mean that the human institution hasn't at times failed to live up to its Founder's principles. However, Jesus Himself promised that the powers of death shall not prevail against it. Given a choice over the skiff of sola scriptura, the ferry of sola fide, or the dinghy of predestination, I'll gladly choose the barque of St. Peter.