This is an insightful piece by an intelligent observer of the battle between historic and progressive Christianity, and I think his conclusion is essentially correct:
The historic Christians believe their religion is revealed by God in the person of his Son Jesus Christ, and that the Scriptures are the primary witness of that revelation. They believe the church is the embodiment of the risen Lord Jesus in the world and that his mission to seek and to save that which is lost is still valid and vital. Historic Christians believe in the supernatural life of the Church and expect God to be at work in the world and in their lives.
Progressive Christians believe their religion is a historical accident of circumstances and people, that Jesus Christ is, at best, a divinely inspired teacher, that the Scriptures are flawed human documents influenced by paganism and that the church is a body of spiritually minded people who wish to bring peace and justice to all and make the world a better place.
I realize that I paint with broad strokes, but the essential divide is recognizable, and believers on both sides should admit that “historic” and “progressive” Christians exist within all denominations. The real divide in Christianity is no longer Protestant and Catholic, but progressive and historic.
When I say “divide” I should say “battle” because both sides are locked in an interminable and unresolvable battle. Interminable because neither side will yield and unresolvable because the divisions extend the theological and philosophical roots of both aspects.
However, it is true that if you look at the dynamic of progressive Christianity, you will see that by the end of this century it will have either died out or ceased to be Christianity.
At this time, modernism still wears Christian clothes in the mainstream Protestant churches and in parts of the Catholic Church.
This cannot last much longer for 11 very simple reasons:
The most powerful reason, of course, is that progressive Christians do not actually believe in the supernatural, which means that in the most basic sense, they cannot reasonably be described as Christians at all.
Michael Sebastian makes much the same point, in rather less elevated language, on Return of Kings:
This message that God promises people a wonderful life has had a deep impact on the lives of many modern Christians. It is a message that fits perfectly with our hedonistic culture that puts pleasure above duty. Christian couples forego having children so they can travel or drive luxury cars. Lukewarm Christian women divorce perfectly good husbands in pursuit of the Prince Charming they think they deserve. Bishops and pastors preach only those parts of the gospel that make them popular with the secular culture.
Modern Christianity is also compromised in other ways. Rather than standing against the culture, Christian churches have tried to accommodate as much of the culture as possible. Some denominations have embraced Christian feminism, push for left wing social causes such as open borders, and bless gay marriages. For that reason, if you want to learn what real Christianity is, you will have to ignore recent teaching in favor of the past. A good rule of thumb is to simply avoid reading Christian material written after 1900. Listen to your Sunday Sermon but take it with a grain of salt.
Repent. Return to the fundamentals of the faith. Read the Word. Preach the Gospel. Go forth and multiply. And ignore all who tell you to follow the world on its broad and easy path to Hell.