I brought up Bertrand Russell’s criticism of Kant in his History of Western Philosophy, and here’s a brief defense of what Kant was likely trying to do:

David Hume’s metaphysics were penetrating enough, and as Wikipedia (the absolute authority) has it:

“Hume thus concludes that our inductive practices have no rational foundation, for no form of Reason will certify them.”

We come to know the world very well through inductive reasoning, but this is not connected to our reason according to Hume, it is merely an intuitive and experiential means by which we understand the world, which is in turn enfolded by Nature. 

Kant speculated that this argument can lead, if one follows it, to a denial of reason itself, and more importantly, a world we are actually coming to know outside of ourselves.   Kant did more than any philosopher to categorize our own intuitive processes to show the limits of our reason,  but he also believed we could come to real knowledge of things (the problem is his arguments for empirically real things aren’t so good) through our reason.  His critique is merely a survey of what he thought those limits of reason were.

As Russell has Kant, he’s merely yet another philosopher floating somewhere between science and religion, doing a lot to update traditional metaphysics, theology, thinking about science…and other fields…but errantly placing reason upon a pedestal of transcendence as have so many before him (not least of all because of the Germany he was a part of).

Kant probably thought he was saving science from the errors he saw in both Hume and Leibnizian rationalism. 

Here’s a Rationalism/Empiricism page at Stanford which says much of what I’ve tried to say here…probably better.