It would also enhance gridlock within various EU bodies and structures that require unanimous approval of all member states. (One of the issues they've had to m

It would also enhance gridlock within various EU bodies and structures that require unanimous approval of all member states. (One of the issues they've had to manage with the several Brexit extensions is how to make sure the UK doesn't make it impossible for EU institutions to run by deciding to veto things.) It's best for the EU to not have two member states with a major, fundamental dispute about sovereignty. And of course, due to the aforementioned rules about unanimity, if Catalonia were to obtain independence their admission to the EU would be entirely dependent on Spain's acquiescence.