The EU has a combined GDP more than 10x that of Russia. Russia has some advantages -- having one of the world's biggest nuclear stockpiles means that they basically get to pick their conflicts, and being an arms exporter means their military R&D is in some sense subsidized by other countries, but still, that's a pretty big deficit to make up. And they have notably not picked any conflicts that the EU would find existential.

They are just set up differently. The EU doesn't have a central military, so they can't do foreign adventures very well, and as a result they don't invade places very often. But this could be seen as a good thing...