The Transcendental Dialectic part of Kant’s Critique of Pure Reason is mainly concerned with negative conclusions about traditional metaphysics, after the positive conclusions of the Transcendental Analytic. Some sections of the Dialectic, like his arguments about the soul in the Paralogisms and about rational proofs of the existence of God in the section on the Ideal, seem sound, while others, like the overall thesis of the Antinomies that reason necessarily produces contradictory conclusions about cosmology, seem very forced.
Kant’s notion of “dialectic” as essentially generating illusions rather than as the antidote and testing ground for illusions seems unfortunately grounded in little more than early modern anti-Scholastic prejudice (but see Self-Evidence for an alternate or complementary explanation based on the difference between dialectic and demonstration).
I thoroughly agree with his main point that the role of pure reason is not to give us new truths about the world, but to be concerned with higher-order interpretation of experience. I also think the various illusions he points out do seem like illusions, but they seem to me more like tacit assumptions deriving from specific historical cultural formations than inevitable accompaniments of the use of reason. (See Aristotelian Dialectic; Mediation.)