I've contributed edits to maybe a dozen or so different Wikipedia articles, and would like to contribute more, but it's hard to get past a couple of hurdles.
The main one is the byzantine and archaic editing tools. The markdown language that Wikipedia uses is a PITA to learn, and following a discussion on the talk page is almost impossible. Wikipedia presents a wonderful UX for browsing and reading. It has perhaps the worst UX I've ever seen for a beginner who wants to make a contribution.
Beyond that, I spent a significant amount of time editing some articles on a fringe religious group that I had studied extensively. (Apart from the group's own leaders, I arguably knew more about the group than anyone else in the world.) But the group that was the focus of the article kept backing out my edits and replacing them with propaganda. It was simply too much work to fight them (especially with the horrible edit/discussion tools), they were a lot more motivated than I was, and I eventually gave up.