I don't think that's true. Much of the point of the first Critique was to vindicate experience as a source of knowledge, for which he thought he needed to appeal to certain synthetic a priori propositions (like causality). When we at LW appeal to causality as a necessary part of the map, but not necessarily a part of the territory, we are making a similar move. Kant was the great enemy of metaphysics.

About morality, you're largely right, though a fair bulk of his writing on morality consists of discussions of social practices and law.