More important would be the question of why are the full Gospel, non denominaltion Christian churches growing by being filled with former Roman Catholics and former liberal main stream men and women?
The answer to that is simple, they, the Full Gospel Christian churches, base their practices and preachings on unadulterated Scripture.
Since they generally use a fragment of the bible (there are 7 books missing) and usually a bad translation (the King James might be good poetically, but a lot of meanings have been changed), I wouldn't say that.
People are looking for guidelines to follow and a community that follows the same guidelines. There are those of us out there who are Catholic who follow traditional guidelines and we don't let the modernists destroy our relationship with God and His Bride.
And the Catholic Church is now filling up with former protestant ministers who have pursued serious inquiry into the first christians and found that the Catholic Church has the fullness of the faith. The catholics who leave were poorly catechized or not at all.
Your opinions as to the meaning of Scripture are just that: opinions!
The answer to your question as to why apostates from Catholicism are found in the pews of "Full Gospel", non-"denominational" Christian churches is that it is a human failing to adhere to simplicity and to easy and self-satisfying ways. It is easier for each Tom, Dick and Harriet to find what they want to find in misinterpreting Scripture than to adhere to an objective moral code that is the product of Scripture and the best in Christian thinking over nearly 2,000 years. The liberal/leftist type of AmChurch pseudoCatholic bishops have failed to adequately catechize many Catholics who then find themselves attracted to theatrical whoopdedoo from the pulpits (if any) of the "non-denominational" churches, including speaking in tongues and whatever. Your churches of that sort aren't skimming much in the way of adequately catechized folks off the Roman Catholic Church despite its evident administrative challenges.
These "Full Gospel" churches are not even "Full Gospel" in that they deny the sacraments that, for the most part, they lack the apostolic succession to convey, cannot provide the Mass, deny the Real Presence of Jesus Christ, Body and Blood, Soul and Divinity, in the Eucharist, etc. No Catholic who IS a Catholic will EVER trade such things for superficially satisfying sermons and Bible studies. As to former liberals who convert to such churches, one is tempted to say that they have already proven, as former liberals, that they will believe anything. Are you an apostate from Catholicism like so many who post such things as you have???
Your God and mine gave us free will. Many exercise it by belonging to the Roman Catholic Church founded by Jesus Christ upon Peter and permanently guaranteed by Him as the trendy insight congregation of last week's Bible study is not. Others find their way to evangelical and penteccostal denominations or "non-denominational" churches and, I will concede, that those churches are better than none and often lead their congregants to a substantial compliance with SOME of God's will.
Despite all the fire and fury between Roman Catholics and other Christians such as you, we agree on much and disagree on little. The disagreements are important but so are the agreements. In a society as degenerate as our own, we have a long way to go to earn the right to dispute one another in the public square for the entertainment of our mutual enemies and His.