If a nation is not able to devote enough money to wage war against all of it’s rivals at once with the realistic possibility of prevailing then it has de facto lost it’s sovereignty, since it is then relying on allies for it’s own protection and is therefore unable to dictate the terms of their assistance.
I think it is becoming clear that all European nations have been in this situation for decades and the only reason they retain sovereignty - to the extent that they do - is because they are all in the same boat.
There are no rivals near by in europe.
And this is exactly why all those militaries havn´t stocked up huge amount of weapons.
Just for example Denmark is not in danger to lose its sovereignty because of the simple fact there is no country near by who would attack them.
Of course if you want to play war in north africa those weapons would be needed.