Which begs the question, why should the EU see China as an adversary? That's mostly an American thing, the Pacific doesn't really concern us.
Maybe alliances will reshuffle in the future?
From the fall of the Berlin wall until the Ukraine invasion, the US saw Russia as more of an adversary than Europe saw Russia.
Yes, even after Russia annexed Crimea. In fact, it's only this year that Europe has started to significantly increase defense spending, three years after Russia invaded Ukraine. And, even then the most aggressive increase plans end up short of where spending was during the Cold War.
Every US president after Clinton (and maybe Clinton as well) urged European countries, especially NATO ones, to keep funding defense and they cut instead.
It turns out that the cowboys were right, that there was a bear in the woods, and that "soft power" wasn't power.
But I don't think that this makes EU policy necessarily incorrect: Would German military spending of 5% GDP have prevented the Crimea annexation?
We won't know, but I don't think so, and European militarism in the 2000s might have led to significantly worse outcomes than we actually got.
I also think that painting this as a clear "US stance proven right in hindsight" is an outsized claim; EU military spending only really came up under Trump, and was a very minor topic before. You could make a similar argument that "the cowboys" were all wrong with the whole middle-east interventionism thing (in Afghanistan and Iraq), but the military side of that was at least competently executed (unlike Russia in Ukraine), collateral damage lower and war crimes somewhat minimized/prosecuted.
I sadly agree that Costa-Rica-style pacifism appears a non-viable approach for the EU now despite looking somewhat workable 15 years ago.