Having experienced it myself, I tend to agree with the general point that getting started with Emacs is not helped by the online resources available.
However, I don't think it is constructive to wish that EmacsWiki would die in order for something better to come up. We are all free to start another wiki, built on any cms we prefer, and if MediaWiki is your choice, go for it. Assemble your moderators, make it better than anything EmacsWiki has provided to date, and you'll be the darling of the Emacs community. That would be constructive. :)