First - change EU to Europe and the point is more clear: 'Europe' failed to defend itself.
Second - Though you're right, EU is not a defensive pact, it's inexorably irresponsible for EU to not provide for defence. Defence is an existential concept - one that involves parts of the state.
How can there be 'ever closer union' and 'open borders' if nations can't even provide for their own defence.
This is 100% clear with Germany's 'sellout' to Russia: Germany, the leading 'political' block in the EU, gave Russia massive leverage which has put Estonia, Latvia etc. at huge risk, and effectively handed over Ukraine do the hungry dogs.
In that dsyfunctional dynamic, 'Sovereign Europe' is still dependent on the Anglosphere: USA, UK and even Canada (!) all of whom have provided much more support than France, Italy, Spain etc (!) in defence of Europe.
"People seem to forget what inflation looked like for their national currencies of these countries before getting the Euro and it was not very green. "
"If they wanted less integration they could have not adopted the Euro just like a number of other countries."
Inflation is much more preferrable than the current straight-jacket death of a hard currency. The lack of inflation relative to Germany is killing Europe.
As for 'adopting and not' - there's no way for them to adjust otherwise. The EU is a 'one size fits all' regime and also a 'Hotel California' (i.e. cannot leave) game.
The Euro won't work without political and fiscal integration and that will never, ever happen, so it's probably better to find something a bit looser.