The EU does have air defences and QRA. Eastern Europe is more at risk from this. And then the question people keep failing to ask: "now what"? Russia is then fully at war with Europe and an open field for air strikes.
It is a ballistic missile which has precision to barely hit a city. Which is fine if you will put 1MT nuke on top of it. However there are no conventional warheads for that missile, so it can't even do any damage and thus it is completely useless.
Russia's definition or the western concept of land grab.
Putin laid it out very clearly in his speeches. They are not interested in a land grab, they want to denazify The Ukraine and liberate the Russian speaking regions.
Denazification means more banderaites and by extension no more NATO.
Target has been conquering Kyiv and installing pro-russian vassal government like in Belarus. He tried to, as we have seen first 3 months, but spectacularly failed.
Everything after first 3 months is grinding war to save face without a clearly defined target.
Oreshnik alone could decapitate the EU in under 30 minutes.