Earlier quoted context omitted.
When educators say that Wikipedia is not reliable, what they usually mean is that serious work should be based on primary sources, not secondary sources like Wikipedia or any other encyclopedia. Wikipedia is good for casual research, and in practice, I found the English Wikipedia very reliable, at least for scientific topics, but it is also pretty good on big controversial subjects. Reliability only starts to drop on…
No, they genuinely mean it's unreliable. Obviously popular articles are great -- they have so many eyeballs and editors that they're not just quite accurate, but often more comprehensive than other sources (in terms of describing competing schools of thought, for example). But when you really drill down into more niche articles, there's a tremendous amount of information that is uncited or not found in the citation,…
Wikipedia absolutely cites primary sources (as well as secondary and tertiary sources), and this is in accordance with their policy. Breaking news stories and scientific papers are some commonly used primary sources. You may be thinking of their "no original research" policy or their warnings against editors adding their own interpretation to primary sources.