Moodle is massively customisable throught its modular design that allows the creation of plugins. You can utterly transform how Moodle looks and behaves without touching the core code. It is what I do for a living for one of Moodle partners, as do many other developers.
Be aware that Moodle is significantly more complex than Wordpress. A fresh install of Wordpress creates around 12 tables (or it did a year or so ago). A fresh install of Moodle installs around 300 tables. The number of tables is not a perfect metric of complexity but it does give you a broad idea.