If scholars find some claim on Wikipedia and repeat it in their published work, they should unquestionably cite Wikipedia. When scholars fail to cite Wikipedia, a few years later other Wikipedia editors come back and cite that work as evidence for the original claim, sometimes for claims that turn out to be nonsense, and people trying to figure out what happened won’t notice that the citation chain is a circle. Cf. https://xkcd.com/978/

Teaching students not to cite the sources they use is a horrible teaching practice which does harm to academia. Better is to teach students to critically examine every source they use and consider its limitations (in Wikipedia’s case, being a volunteer project by a wide range of pseudonymous strangers), follow up on claims made there, check other sources for contrary claims and analyses, etc.

Every source has biases and limitations. You can find plenty of fabrications and distortions snuck into e.g. New York Times stories, undergraduate history textbooks, or Supreme Court decisions. These sources should also be examined critically.