Wikipedia's antisemitism has personally caused me more problems than any other single entity.
Someone will talk about the "evils of Zionism" and I will say "Let me clear up some misconceptions on what Zionism is, as a Zionist".
Then the antisemite will say "WIKIPEDIA SAYS IT'S THIS!!!" and then quote Wikipedia's antisemiticly biased article on Zionism.
Why is this antisemitism and not anti-Zionism?
The article is anti-Zionist, and contains several falsehoods, but it's not merely one article, it's a collection of articles on Jewish topics, on Zionism, on Israel, etc. It's demonstrated to be a coordinated effort, and it's relatively new- the same articles were not this way just a few years ago (before 10/7).
In the meantime, Wikimedia has taken the position that Jews do not get to define their own beliefs and are not trusted sources on these topics- as illustrated by policies saying that the oldest, and one of the largest anti-hate group in the US is not to be trusted.