Fairy Tail, named after the Fairy Tail guild itself -- the most powerful and famous wizard guild in the fantasy nation of Fiore -- follows Lucy Heartfilia, a Celestial Wizard set on joining the guild and embarking on an adventure after running away from her stifling, wealthy homelife. These few sentences encompass the majority of the Fairy Tail's meaningful world-building, which is a real missed opportunity.
Fairy Tail introduced many new characters and places for Lucy to meet and visit, but fans might wonder if mangaka Hiro Mashima could have, and should have, done more to explain the nation of Fiore and the Ishgar continent as a whole.
Fairy Tail Is Really About People & Relationships
A fantasy action-adventure series like Fairy Tail is the perfect setting for some serious worldbuilding; that is, fleshing out the details of the world the story takes place in. Fairy Tail does its share of worldbuilding, but only enough for Lucy and Natsu's adventure to proceed, not enough to create a fully-realized world. Everything established about Fiore is in service of allowing the wizards to meet new people and explore their relationships.
Given the length and genre of Fairy Tail, this series could have deepened its world far more, along the lines of its shonen contemporaries. As it is, Fairy Tail focuses most of its energy on big battles and, more importantly, its characters. Often, a character's backstory doubles as world-building, as with Irene Belserion, but more often, the details of what it's like to live in Fairy Tail's world are used to develop characters and set up fight scenes, with worldbuilding for its own sake being a distant priority.
While a character-focused route is a legitimate path to take, dedicated fantasy fans might be disappointed with how thinly Fiore and the Alvarez Empire are developed as worlds. Focusing mainly on characters and relationships does give Fairy Tail its own flavor as a series, while also thematically living up to the guild's central values and driving the plot, but it does little else for the series. For example, the Phantom Lord guild once attacked Fairy Tail, not for any deep lore reasons, but because its master, Jose Porla, had a personal grudge against Guildmaster Makarov and wanted to settle the score.
Later, Lucy and Natsu meet Warrod Sequen, one of the Ten Wizard Saints. Warrod's introduction served not to deepen the world of Fiore and its magic system, but to explain how the Fairy Tail guild came to be, and the nature of the founders' relationships to one another. Even the introduction of the series' main villain, Zeref Dragneel, served to deepen that character and his relationship to Mavis Vermillion, not the world he came from. At most, Zeref's backstory briefly established the existence of a Greek-inspired school, complete with togas.
How Fairy Tail's World-Building Compares To Similar Shonen Series
Many shonen series have a heightened focus on worldbuilding, and some have set a high bar on how it's done, balancing character development with establishing their reality. One Piece is arguably the best example, as mangaka Eiichiro Oda provides tons of context for nearly everything that happens in the manga, thoroughly fleshing out the many cultures and civilizations that appear throughout the world, going so far as covering the history and geography of the world in-depth. This is one reason why One Piece is so popular: Luffy and his crew are exploring a world that actually feels like a place people live and have lived. It's not just a tool for setting up action sequences.
Naruto also thoroughly builds out its world, taking its time to reveal things as they become relevant. At first, the Hidden Leaf Village is the main setting for this story, but before long, it's made clear that the Land of Fire is a huge place, and is one of many nations on a continent full of them, from the vast desert of the Land of Wind to the rain-soaked, miserable battlefield that is the Land of Rain.
Naruto's worldbuilding may isn't exactly on One Piece's level, but it's still more extensive than Fairy Tail's, complete with international politics that help explain why shinobi wars happen and why groups like the Akatsuki, for example, rise to power. Nagato, Yahiko and Konan hated how the Land of Rain was just a convenient battlefield for larger, feuding nations, and seeing all that pointless violence and death led them to create the Akatsuki to bring about world peace. Now that's some efficient world-building.