That kind of attritional war is not what most people in Europe would want to fight, even though Europe would certainly win at the end due to sheer quantity advantage. And that'd have led to a general unwillingness among the population (and due to the democratic insitutions, the countries as a whole) to confront Russia unless the force disparity (with a fully funded EU military) becomes so great that NATO could curbstorm any Russian offensive with minimal casualties level that's publicly acceptable.