The "dismal" performance of the EU has happened in large part because of the global financial crisis or the "Great Recession" that has slowed world economies since 2007. This economic crisis has led to problems that are collectively known as the EU's "debt crisis."
This crisis started to be visible when Greece came to be in danger of defaulting on its loans. This led investors to wonder about the safety of loans to many other EU countries such as Spain, Portugal and Ireland. As this has happened, people have started to worry about the stability of the Euro. This has meant that Eurozone countries with stronger economies have been called on to bail out the Greeks and other nations. There has been considerable political opposition to this in rich countries like Germany.
In this way, the global financial crisis has led to a dismal economic and political performance on the part of the EU and some of its member countries. They have been unable to agree on ways to reduce their debt or ways to help other EU countries that are in economic trouble.