Rationalism is the belief that knowledge comes from pure reason. Humans are rational creatures; we have innate knowledge and reason that we can use to find the truth. Knowledge cannot come from subjective experiences or our senses because reason will eventually bring us to truth. Is rationalism a reliable way to find truth?
Reason cannot be a method of gaining true knowledge. Reason constructs knowledge or new information based on innate knowledge embedded in us that is subjective. For example, our knowledge of what is good or bad depends on the socially constructed principles of morality that can vary with time and location. Commonly held cultural beliefs and other opinions may impact reason which leads to inconsistent knowledge. Assuming we have innate knowledge that is beyond doubt is flawed. Building knowledge upon innate knowledge is subjective. Believing this assumption leads to superstition because innate knowledge is not evaluated or proved. Everything needs to be questioned and not be based on assumptions and interpretations. The only method that allows for accurate questioning and evaluation of answers is by collecting empirical data. Empirical methods are the most accurate ways of gaining knowledge. 
Rationalism can tackle questions that science cannot address. There is knowledge beyond sense experiences that humans can only achieve through innate reason and common sense, like questions on morality and other philosophical questions that are still outside the realm of science. Reason is still necessary to gain knowledge.
Reason can be backed by a warrant: a proper justification for a belief that prevents superstition. If people are able to come up with justifications for their beliefs, then their beliefs are reliable. Philosophers are still trying to map the nature of the warrant more specifically. Reason backed by proper justifications prevents superstition.