I think it was very poorly worded, tbh. Because the paragraph reaffirms what is the essence of Just War theory, that is, that war is just when it constitutes proper defense from attack:
192. To all of this, the media and digital dimensions are adding new and decisive elements. Communication networks, fragmented information environments and algorithms that reward conflict can magnify polarization and resentment, increase propaganda and make shared discernment more difficult. Thus, war is not only fought, but also culturally conditioned through simplistic narratives, a friend-or-foe mentality, disinformation and fear. When historical memory fades and the ethical principles that protect civilians and the most vulnerable are weakened, it becomes easier to justify violence as necessary, inevitable or even “sanitized.” It is in this context that humanity is slipping into a violent culture of power, where peace no longer appears as a responsibility to be taken on, but as a fragile interval between conflicts. Today, more than ever, without prejudice to the right to self-defense in the strictest sense, it is important to reaffirm that the “just war” theory, which has all too often been used to justify any kind of war, is now outdated. [182] Humanity possesses far more effective and capable tools for promoting human life and resolving conflicts, such as dialogue, diplomacy and forgiveness. The use of force, violence and weapons reflects a relational poverty that always has disastrous consequences for civilian populations.
The note is also important in this sense:
Cf. Francis , Encyclical Letter Fratelli Tutti (3 October 2020), 258: AAS 112 (2020), 1061: “In recent decades, every single war has been ostensibly ‘justified.’ The Catechism of the Catholic Church speaks of the possibility of legitimate defense by means of military force, which involves demonstrating that certain ‘rigorous conditions of moral legitimacy’ have been met. Yet it is easy to fall into an overly broad interpretation of this potential right. In this way, some would also wrongly justify even ‘preventive’ attacks or acts of war that can hardly avoid entailing ‘evils and disorders graver than the evil to be eliminated.’”
So, it seems to be what is being criticized is the spurious attempt to weaponize just war theory to make anything you do appear as legitimate self-defense (If we don't take over Greenland the Russians or the Chinese will, and then attack us, so conquering Greenland is an act of self defense!). Which is also something anyone who studies these things even half-seriously knows and agrees with. "Preventive" strikes are most certainly NOT considered just by any reasonable just war theory.
Another sense in which Just War theory needs readjustment (which, again, acknowledged by pretty much everyone who actually studies the issue) is that our capabilities for destruction, and specially for the harming of civilians, have grown exponentially in the last century and a half, and so proportionality means a much different thing than it did for Augustine or Aquinas.
All that said, I also don't think Leo will elaborate on this. John Paul II and Benedict XVI did write their own encyclicals for the most part, because they were both academics, but neither Francis nor Leo are such. So these documents are mostly written by commission or commissions, and then read over by the Pope before publication. Some sections might come directly from his pen, but I suspect this one wasn't specifically his (he tends to avoid harsh and imprecise language, and his general writing style is clean and straight to the point, which this is not). We'll see.