This article reads as if this person seriously believes that ... Europe and European trade (strangely not the US, but okay) is the only thing preventing just and utopian outcomes across the entire world.
It's also a useless discussion: whatever faith you may have in European progressive/socialist parties, they are not willing to give up the prosperity they have. They want fairness in addition to MORE than what the European people already have. If the demand is to give up more than 100% of European economic growth, you will not find them allies. Oh and there's the problem that they've got maybe 10-20% of the vote, and all other parties are not nearly as willing to help.
So these utopian outcomes won't happen. What will?
What these people never discuss is who will replace the US? Because the only real contender is the Chinese CCP. That will, to put it mildly, not be good. Frankly, the absurdly huge distinction between US hegemony and all others, whether you mean British hegemony, Ottoman hegemony or even going as far back as Roman or Greek hegemony is that every hegemon with the sole exception of the US conquered and murdered their empire together using slave armies (to their credit, some European powers, not all but some, at least refused to use slavery)
You might say "but China has promised not to ...". Ok, let's go there. Let's say China doesn't actually go ahead and try to conquer 1/3 of the world. Or, at least somewhat realistically, let's say they take over Taiwan and the Phillippines and stop there. Or let's even say they add Indonesia and Malaysia maybe even Japan to that ... and then stop.
Note: the CCP ideology is authoritarian and racist. We can perhaps argue if they'll go as far as the Nazi's did in the past century, but I don't understand how any rational person can argue it isn't at least going to go quite a ways in that direction. But if you don't live there ... who cares right? Also: if you live in these countries: get the fuck out of there (because the EU is definitely going to refuse to pay for the US securing the seas)
Or you might say you actually believe the CCP, and let's say that you're right to do so. The result is that the US withdraws from the global oceans ... and that's the end of that. What will happen?
The problem is "multilateralism" was demonstrated EXACTLY what it was at the end of WW1, at the real ending of Colonialism (I mean that yes, colonies endured a bit more, but the economic domination of European powers ended there. Their last big hurrah. At that point European Colonial powers had enjoyed a large surplus but right there and then, it was gone, and that's the point where the decline became totally inevitable, and exactly what happened became a certainty: a very large, protracted, slow economic decline. We might also mention what people chose to do in response to this happening: WW2)
This is not theory. This is history. This is what actually happened. Any rational person should at least consider it might happen again.
But let's discuss what will happen to us. Because that's what matters, right?
First, perhaps most obvious, piracy will return, at the very least to East and West African coasts, maybe even the African Mediterranean coast, and to Malaysia and Indonesia, as well as parts of India. None of the countries there have any hope in hell of securing their own coast, never mind international waters. Quite a few will participate in piracy like they did before. As a result international trade will largely collapse.
Maybe EU-US trade will survive, and maybe even US-China trade. But EU-Africa? EU-China? It will at the very least become orders of magnitude more expensive.
Second, a large list of countries (a growing list, I might add) that are at each other's throats but are currently being stopped either directly by the US army, or by US weapons and diplomacy, and even some being restained by EU weapons and diplomacy, will burst out into ethnic violence. We'll have 10, or god forbid 50, Sudan-style conflicts. There is even such a conflict brewing in the EU: Kosovo - Serbia ... nothing is solved there and while people aren't currently at each other's throats, they're not far from it (and if you're truly honest, the problem is Kosovo. Or put it this way. If you erased Serbia from the map, the Serbia-Kosovo conflict would continue. If you erased Kosovo from the map, the conflict would stop). Greece and Turkey ... they're perhaps further from war than Kosovo, but I would still argue that left to their own devices, another war there is inevitable. India-Pakistan. China vs essentially everyone. And so on and so forth.
The problem is "multilateralism" was demonstrated EXACTLY what it was just after WW1. There is a large group of countries that when restraints on their actions are released ... the result is a large set of genocides all occurring at once. I'm a pessimist, but let's be honest: this will simply happen again.
That is at the very least a big risk of what Piketty and other calls "justice". And the problem is simple: for at least the next few years it is extremely in the EU's and EU member states' financial interest to bring us closer to this scenario. Piketty is arguing for social justice, and he should: we need that. We need that influence, because other forces are looking to destroy the rights we currently enjoy. But they'll never talk their way into more than minority influence in "the West".
Perhaps Trump and MAGA are just extreme and cruel fatalists who realize what is coming now: a large, protracted, worldwide economic crisis, caused by Europe and China, followed by WW3. Perhaps they simply think the US will win WW3 and the world will go back to 1950. Perhaps their theory is that the best idea for the US is for WW3 to start before this economic crisis really hits the US, that the only thing they need to do is to withdraw the US army, weapons and diplomacy currently standing between a great many adversaries.
Hell, that may be exactly what happens. But this is both giving these people way too much credit AND ignores that of course WW3 will make the world suck pretty fucking bad for a long time.