MediaWiki has a lot of extensions, but Wikimedia wikis don't install all of them. WordPress has a lot of plugins, but the Wikimedia blog doesn't install all of them.
With Phabricator, I think we should re-examine and prune, if needed, the installed Phabricator applications. Looking at tasks such as T106924: Consider using the Badges application for a few special roles to highlight those users' comments and tools such as https://phabricator.wikimedia.org/phurl/, a URL shortener, I'm questioning the virtue of having these applications installed.