Long story short, probably the most remarkable contribution of Kant's Critique of Pure Reason is the notion that the subject plays an important role on the definition of the object.
However, if the subject defines the object, and if the discipline that deals about all such subjectivity (Metaphysics) is considered a pseudo-science, then, science would be at risk. Having Kant noticed many flaws in metaphysics, he aimed to raise metaphysics to the level of science. If science and metaphysics were at the same level of formality, scientific knowledge would be safe.
So, in order to address the lack of formality of metaphysics, Kant proposed a solution: the Transcendental Doctrine of Elements, the starting point to any possible formalization of metaphysics. A large part of the Doctrine's solution is to identify all pure (synthetic a priori) metaphysical knowledge. I assume that he expected his followers to use such truths to build a metaphysical formalism and produce subsequent theorems.
So, he proceeded as follows.
In the Transcendental Aesthetic, Kant found that time and space were pure metaphysical knowledge. In the Transcendental Analytic, Kant found more pure knowledge: the twelve categories.
However, in the Transcendental Dialectic, Kant wasn't able to identify any form of pure knowledge. What this means is that knowledge that raises on the Transcendental Dialectic context leads to antinomies and contradictions. This, because speculative metaphysical reasoning, attempting to go beyond the limits of possible experience can lead to contradiction.
I personally never agreed with such position. Moreover, this is not a trivial assertion and for me, it's extremely destructive.
The fact that Transcendental Dialectic knowledge lead to contradiction logically implies that any possible knowledge in the Transcendental Dialectic is contradictory (principle of explosion emerging not at one, but in multiple points of the logical structure). If there is some possible logical consistency in the Transcendental Analytic, then, it is false as well.
But not only that. Science is essentially the description of empirical facts, science searches for empirical truth. Scientific knowledge goes beyond the limits of possible experience, which for Kant would lead to contradiction and antinomy.
So it appears, in consequence, that Kant, instead of raising the level of Metaphysics to the level of science, is lowering science to the level of a pseudo-science, along with the current state of metaphysics.
An interesting ---while trivial--- additional consequence is this: given that Kant's work can be mostly qualified as Transcendental Dialectic knowledge (since it is not pure, since it is viced with rational constructs resulting for the most part of facts of experience), then, Kant would be denying its own work. Kant would self-destruct himself.
Modus Tollendo ---and this is my personal approach--- if Kant CAN assert that Transcendental Dialectic knowledge leads to contradiction, if such is an a posteriori truth, then there must exist a fundamental, common and objective Transcendental Logic metaphysical truth which we all use as reference to accept science and even Kant. I cannot qualify such truth as dialectic, since Kant uses the term dialectic in a classical old sense, meaning a contradiction with no solution. Evidently, my solution is irrelevant here because it is speculative. I just want to detect the flaw in Kant's argument.
Is this analysis correct, or which are the mistakes on it?
Before formulating your answer, consider this: if you accept the Transcendental Doctrine, then, you accept that your own answer is an a posteriori dialectic judgment, and therefore, your own answer is antinomic (contradictory), that is, it is self-destructive (easy to prove). That is the problem to solve. My approach is to consider Kant is wrong about it, and that there MUST exist some Transcendental Dialectic pure metaphysical truth*... which is the one I base upon to sustain this very assertion, to fix Kant's self denial and to sustains science, which becomes non-antinomic, so it is the actual empirical truth.
* While I can identify one, it is out of topic here since it would be an opinion.