Religion has three main interdependent elements: narratives, practices, and experiences. What you're essentially pointing out here is that with regard to a particular concept (in this case demons), those three elements might not be in perfect agreement. That's a valuable insight. It can also be applied to e.g. grace, sin, death, salvation, angels, healing, heaven, or God.
Skeptics tend to overestimate the importance of the narratives or their qualities (e.g. whether they are internally self-consistent, or genuinely scriptural, or morally good) while underestimating the importance of practices and experiences. Hence, are constantly surprised and frustrated at the failure of religion to disintegrate when the narratives are ably challenged, even when the narratives are acknowledged false or incomplete or "not literal" by adherents.
The prevailing Christian narrative of (the origin of) demons might speak of fallen angels (which doesn't come from the Bible but from Milton and other sources), while the practices regarding demons (such as repelling them by ringing bells, or exorcism) treats them more as spooky monster parasites, and supposed direct experiences of demons (such as overcoming addiction) feel like cravings and strong destructive emotions. These are not terribly consistent; why would a fallen angel want to possess a human; why would a spooky monster parasite feel like a craving for a chemical; and so forth?
Any answers to those questions only add retcon details to the narrative element. (Fallen-angel demons hate humans because they're jealous of God's favorable covenants with humanity, making them want to prey on weaker humans and drive them away from salvation!) This happens because no amount of criticizing the narrative really has much impact on people's perceived experiences, nor on practices. There are many churches that have ditched (or never had) the superstitious belief that the sound of bells drives demons away, but most of them still ring bells because that's a Christian-y church-y thing to do.
