Wikipedia is extremely accurate with facts. While errors can be introduced either intentionally or erroneously they will be corrected. For fun google Wikipedia versus Britannica and you will find that for science topics, names, dates etc the accuracy is equal. It is excellent for history, medicine, science, biography.... Like any reference one should never depend on a single source but for people to simply repeat the Wikipedia is unreliable meme suggests they have not done their research.
To its credit there is even a Wikipedia page on the reliability of Wikipedia.
Reliability of Wikipedia - Wikipedia, the free encyclopedia