Agree. Kant was very rational and organized. That said, his Categorical Imperative untethered morality from Christianity.
You could take it one step further back to Descartes, who turned God into a convenient, abstract stop-gap against his infinite regress into “questioning everything.” And (as my old philosophy professor once noted), he set the mind-body problem in motion that has so many of today’s secular intellectuals totally lost in their mental and psychological machinations, unable to get the slightest clue about reality by looking at reality.
It's interesting that the two main branches of western philosophy, analytic and continental, both sprang from Kant.
A number of people place the blame of the beginning of the end of Christian Europe with Descartes and his radical skepticism. Kant seemed like someone who was trying to put back the pieces that Descartes had blown apart.
Others point to Occam with his nominalism that tended to erode away the foundations of scholastic philosophy.
My own belief is that it was the printing press that was the death knell of Christianity. On the one hand it allowed the Word of God to be spread much more widely and efficiently. On the other hand it helped spawn numerous contradictory interpretations of the Word of God which sowed the first seeds of doubt in the populace at large.