While Descartes denied that knowledge begins with experience, I'm sure he would not deny that the senses DO provide the data for some knowledge, provided that data is sufficiently valuated by PURE THOUGHT for its clarity and distinctness.

In the Meditations, Descartes does assert the reality of the CORPOREAL/SENSUAL WORLD, but asserts PURE THOUGHT as a necessary ground for inducing the truth of CORPOREAL claims and judgments.

You also have to understand that Descartes demanded absolute certainty for knowledge. That is, all knowledge must begin from absolute grounds and proceed DEDUCTIVELY (certainly) from there. This demanding view of knowledge is no longer widely held, by philosophers or otherwise, especially post-Hume. Many philosophers in the Cartesian tradition (epistemological foundationalism) hold a sort of "soft foundationalism" that erases the certainty requirement, while many others consider foundationalism to be impossible (infinite regress).

That is why Descartes was a rationalist. He found that the only way to establish and absolute foundation was with the COGITO, the 'I' that persists through any SKEPTICAL SCENARIO. Building up from this foundation, deductively, we can then INCORPORATE experience into the knowledge by arguing from the basis of the COGITO, the absolute subject. Of course, this is riddled with all sorts of other problems but that's another thread.