In Episode 117 of the Anime World Order podcast, Daryl Surat, Gerald Rathkolb, and Tim Eldred briefly discussed the idea that, in order to modernize a classic, the creators of Space Battleship Yamato 2199 gave its protagonist Kodai Susumu a less gung-ho personality to match the current male audience for anime. Daryl pointed out that such heroes were the exception these days, and gave Eren Jaeger from Attack on Titan as an example of someone cut from an older cloth in terms of shounen main character tropes. I agree with the overall statement, but I also find that Eren works especially well as a protagonist in this current age because of the perspective it provides for his actions and personality.
The character of Eren Jaeger is essentially a boy who has dedicated himself to a singular goal in life, to wipe out the enemy Titans that destroyed his village and killed his mother. Characters in the series point out his immense drive and the willingness to work hard to accomplish his desires, and in this sense he exhibits the same qualities as many of the most famous shounen heroes. However, unlike Naruto whose overwhelming personality and “act before you think” approach is generally seen as a positive and the source of his series’ fundamental themes (heart is what’s important for instance), Eren Jaeger’s similar mindset is shown to have not only strengths but also critical limitations.
I see Eren as the kind of guy who makes people better than him feel worse for not accomplishing as much. Aside from his transformation, Eren is shown as not being particularly exceptional when it comes to fighting Titans, but he’s more willing to just go and do it, and not let his fears get the better of him. This is mainly what drives his relationship with Jean, as Jean is clearly smarter, wiser, and comparable in physical ability to Eren, but lacks his ability to throw himself into danger. On the other hand, Eren’s narrow-mindedness is the reason he can’t accomplish everything on his own, and that if he were a leader of men, for instance, he would probably send them all to their deaths just by being himself, as opposed to Naruto who’s supposed to become a leader with pretty much the same personality.
This is what drives the dynamic interaction between Eren, Armin, and Mikasa. Eren’s lack of forethought is tempered by Armin’s strategic insight and willingness to sit back and observe, but Eren’s fearlessness also helps keep Armin from overthinking things or succumbing to self-doubt. Similarly, although Mikasa lacks the vast dreams of Eren and Armin in terms of wanting more out of the world, her cool head and decisiveness help to keep both of them moving forward.
The fact that Eren has trouble transforming into his Titan form in one instance basically comes down to the fact that Eren has vision and drive but lacks perspective. When the Titans were simply an absolute enemy, someone who cannot be compromised with and who must be destroyed no matter the cost, it was easy for Eren to obtain the level of focus needed to become his Titan form, but when it turns out that his enemy is actually someone he considered an ally and a fellow human being, he cannot process this idea due to that same rigidity. It is ultimately his friends, who each see the world from a different place, who help him resolve this issue, and even that comes at the price of Eren having to throw away the basic love he has for humanity.