Wikimedia websites articles could be not bad for some hint or clue, but when are we dealing with mathematics and physics that need to be precise and reliable and provable, referencing to Wikipedia for a scientific issue does not look good, because CryptoSE itself is referenced as some research and if the reference is not reliable how come the reference of the reference should be trusted?
It seems like we need to make a case distinction here. Namely between authoritative and informative references. The former being used as a reference that contains the arguments for a point not made or summarized in an answer. The latter being used as a reference for supplementary information, e.g. to give a quick overview of a topic or to generally give information not important to the correctness of the answer.
I think Wikipedia (and similar projects) are fine as an informative reference but not always as an authoritative one. An example for an informative reference would be referencing the page for authenticated encryption so somebody who has never encountered that term has a starting point. However this page would be obviously unsuitable as a reference for a formal definition of what it means for a scheme to be authenticated encryption.
However there are quite a few pages on Wikipedia which in my view are good enough for us to reference in an authoritative manner. An example for this would be the page for Lagrange's theorem.
So, if you as a user encounter a reference that you are unhappy with because it is inadequate leave a comment requesting a better reference with a short explanation why the current one is inadequate. You can also suggest / make an edit instead if you have a better reference handy, but please first try commenting and suggesting the new one with an explanation; when do you get not response or edit then please document why you replaced a reference beyond a basic "wikipedia bad".