Attack on Titan has established itself as a staple of the shonen action genre, and many fans may consider it an instant classic. At the very least, it casts a long shadow, and it's tough to deny this series' impact overall. But even then, the series can still push things to the next level as Season 4 is showing. This is the Shippuden of Attack on Titan.
While the fourth season is not a true reboot of the franchise, it does act as a sort of reset button for the plot, and there is a clear (and organic) gap between the third and fourth seasons of Attack on Titan. This may feel familiar to many shonen fans, since the Naruto and Dragon Ball series did the same with Shippuden and Dragon Ball Z, respectively. Evidently, it's a formula that works.
How Naruto & Dragon Pulled It Off
Akira Toriyama's overall Dragon Ball franchise almost single-handedly set the mold for modern shonen -- that is, the late 1980s and beyond. It all started with the goofy, cartoony adventures of Goku and his friend Krillin, though the comedy didn't detract from the quality of the action or Mr. Toriyama's imagination. This series was beloved for its balance of worldbuilding, martial arts action, advanced technology, memorable characters and far more, but that was not the end. Once Dragon Ball concluded, the setting jumped forward a generation in Dragon Ball Z, featuring an adult (and somewhat more serious) Son Goku and brand-new adventures.
Goku was a man by then, and his enemies scaled up, too. The stakes became far higher, and Goku and his allies faced devastating threats ranging from the classic Frieza to the ultimate lab-grown Cell and Majin Buu, all with a new tone and new characters compared to Dragon Ball. The series didn't abandon everything that made the original Dragon Ball was it was, but it did take a big step forward in most terms, acting as a true evolution instead of a replacement. This balance appealed to many fans.
Something similar can be said about the Naruto franchise, which launched its first mega-arc with 12-year-old Naruto Uzumaki, the pariah who sought to prove his worth and become Hokage someday. The plot revolved around Naruto's quest for recognition as well as Sasuke's growing ambition and frustration, culminating in the fateful duel between former friends at the valley waterfall. Naruto had lost, but more was to come.
Naruto Uzumaki followed Goku's lead, leaping into a new era and new challenges as an older, wiser, tougher and more mature lead who never truly abandoned what made him who he was. Naruto's quest for recognition was nearly complete, so he set his sights on a new goal: saving the world from the Akatsuki threat and, later, the terror of Madara Uchiha and princess Kaguya herself. Everything scaled up in Naruto Shippuden, from the strength and variety of Naruto's enemies to the techniques used and the scope and scale of it all. And if Goku and Naruto can evolve like this in later story arcs, so can Eren Yeager.
How Eren Yeager Stepped Into A New Era
Attack on Titan's final season is following that basic formula of "new era, new enemies," but with its own twist. This series always had an element of mystery and conspiracy to it, more than most shonen series, and the gap between Seasons 3 and 4 involves a massive revelation about the Marley Empire and the true place that the Eldians have in the world. In this way, it's true that Attack on Titan's ongoing fourth season pulls a Shippuden by replacing yesterday's foes with today's enemies (the Marley Empire), as well as new powers such as the War Hammer Titan, but there is more to it than that. It's not just the action that has evolved, but also the plot.
Attack on Titan frequently places more emphasis on the plot than action in terms of conspiracy, politics, ever-shifting alliances, mysteries and far more. For three seasons, Eren and his friends were certain that they faced an apocalypse wherein humanity's "last" city faced the alien terror of the Titans. But now, in Season 4, all that has changed. It's not a plus-size zombie apocalypse anymore; this is about international politics and war, all centered around the bloody history of the Eldian people and the Marley Empire's attempts to truly dominate the land, including Paradis Island itself. The stakes are entirely different now, and the Titans, once treated as giant zombies, are now patriotic weapons of the Eldian people (mainly through Zeke's rumbling plan), and the true enemy is the Marley Empire, including its brainwashed Eldian warriors and soldiers, from Annie to Gabi Braun and others.
Attack on Titan's fourth season didn't forget anything that came before, but with a massive paradigm shift in the world, new enemies, new stakes and new powers involved, it's clear that Attack on Titan's true Shippuden era has arrived, in all the right ways.