As someone with no firsthand knowledge at all, I am inclined to believe your position is correct. But I also think the Economist is making an important point: Russia's continued prosecution of this war will shred their internal economy with consequences lasting for decades or centuries. What people often underestimate is just how much damage an economy can suffer before breaking down entirely.
But Putin doesn't care about that, so the war will continue until something changes militarily.
The EU is rich enough to support Ukraine for a very long time. During that time it is likely that Ukraine develops better and better weapons. This requires Russian army to improve as well.
It's not clear how the Russian army will improve when the economy declines.
The EU is rich enough but will they stay "willing enough"? Unfortunately, many EU parties that are gaining popularity are also against spending money on Ukraine
The EU, well NATO has the problem what Russia will do when it is no longer at war with Ukraine. There is also the question what the US would if Russia attacks a NATO country.
So European NATO countries basically need to keep supporting Ukraine while they try to becomes militarily independent of the US.
EU just needs to support Ukraine until Russia has dug themselves into a hole that will take generations to recover from. Their might be a point where the war hasn't ended but Russia is no longer seen as a threat by the EU.
One issue is that Europe got caught with it pants down. It likely that Europe will keep improving its defense long after it is no long necessary from an economic point of view. Supporting Ukraine in destroying whatever Russia manages to produce is a sound strategy in this context.
If Russia really becomes weaker and the war winds down a bit, then supporting Ukraine is likely to become cheaper as well. But as long as Russia manages to send tons of drones and missiles to Ukraine, Europe should be worried. So Ukraine will remain a testing ground for air defense for a while.
There is also the issue with the Baltic countries and to some extent Finland. Those countries are terrified that Russia will do something stupid.
The EU as a whole is rich enough, the problem is that its the elites that are rich, not the ordinary citizens. However, the burden of support (via taxes and cutting welfare) will be places on ordinary citizens. Hence, the need to flame the war rhetoric. Still, there is no real support for forever war among EU citizenry.
Even if there is enough support for economic/material support of Ukraine, the matter of sending your man to die on the eastern front is an altogether different matter. Even Poland is not willing to do that. I mean, 'I am afraid of dying in a war, so I better go die in a war, to prevent that.'
But Putin doesn't care about that, so the war will continue until something changes militarily.