The EU will never close tax loopholes since there will always be a veto from the likes of Ireland, Netherlands, Luxembourgh or UK.
Primarily the new rules are based on the existing UK rules and I'm guessing whatever legal changes were required are still going through.
Most matters are done under qualified majority - which is a small super-majority based on population.
A post-Brexit UK going full on offshore tax haven might encourage the EU to get their act together on finance, and come up with some ways to crack down. Well, one can hope...