It boy has the control and influence it’s member states grant to it. The EU can’t unilaterally impose rules on its members, hence Britain’s ability to negotiate exceptions to any EU policies or initiatives we didn’t want to be part of - Working Time Directive, Schengen Agreement, Euro Zone, etc. Tax policy is something EU member governments want to keep to themselves and don’t all agree on, and as long as that it so the EU will have a very limited say in it.