Christianity certainly is an organized religion, according to the definition I provided, and that isn't what Jesus was talking about. He simply said "the gate is narrow and the way is hard that leads to life, and those who find it are few (Matt 7:14, ESV). It would be reading into the text to make it say that Jesus was talking about organized religion, when all he said was "the way." There are those, likely quite a number, who claim to be Christian and attend a Christian church regularly, but are not saved because they haven't gone through the gate.
Paul talks about "self-made religion" in Col 2:23, and while he never mentions religion again, it stands to reason that he is contrasting that self-made religion with all the rules and commands for believers that follow in chapters 3 and 4. In other words, consistent with the definition of religion that I gave, Paul is giving a "set or institutionalized system of religious attitudes, beliefs, and practices."
And James, in 1:26-27, differentiates between worthless and "pure and undefiled" religion. Christianity, properly understood and practiced, is pure and undefiled religion. The point is, there is good religion and there is Bad Religion ?, and Christianity is the good, true religion.