Please. Let's not go all Salem Hysterical.
Um. Friend Karen? Demonology, exorcism and deliverance are absolutely taught in the Catholic Church. You can find it in the Roman Rite, the Cathechism and at least one encyclical that I'm aware of.
Yes. I believe a great multitude of people are in various stages of demonic influence. Possession being a small number. Oppression being slightly larger. Obsession being the largest.
In actuality there has been a great increase in the need for exorcists and deliverance ministry over the last 10 years. So your theory that you don't hear about it is faulty.
In truth though, the devil's greatest trick is convincing people he does not exist. The devil does not want to be known. If people start seeing demons under every bush, they will be far less likely to welcome one in.
Yes, demons must be invited in. But it's not like "knock knock." "Who's there." "Evil demon" "Come on in!"
It's more like - "Oh look, someone left their very expensive sunglasses on this table at this diner. I think I'll keep them." And in walks the demon of greed or the demon of theft.
Fr. Malachi Martin posed the theory that when a fantastic outward manifestation appears, the "target" is not the possessed individual, but the priest. The exorcist.
Such as the famous case "The Exorcist" is based on. After the real exorcism the movie and book were based on, the real priest involved, Fr. Bowdern, was fundamentally involved in desegregation of the Catholic Church.
Segregation is evil. The devil liked it as it was. Since this was the path Fr. Bowdern was on, an attempt was made to tip his faith into despair. To kick him off the path.
Then there are cases which boost the faith of many. Faith in Germany is at an all time low. The case of Anneliese Micheal brought a revival of faith.
But for the most part, demons are subtle. They do little things to make us hate ourselves. To make us hate God. Anything to make us less beautiful in our own eyes so that we might actually believe He could never love us.