While Descartes denied that knowledge begins with experience, I'm sure he would not deny that the senses do provide 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 (Broughton, 2002).
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 ...