Wikipedia editors are petty and incredibly biased. Start reading the talk pages, especially on controversial articles, and your opinion on Wikipedia’s objectivity will rapidly plummet.

Also, it’s a bit like reddit: you find yourself learning so much about new topics, until you start reading about things you have actual expertise on, and you realize the people writing this shit are uninformed idiots, and, when you try to fix the information, the petty nerds who control it revert your changes and ban you.