Even if Turkish-European Union relations were healthy, the nature of the relationship would sooner or later provoke a crisis. We know that a customs union agreement was signed before any chance of Turkish accession to the EU. And before the customs union, there was the additional protocol.
The free circulation of people in certain sectors, which is one of the rights of the customs union, has never been implemented by the EU. Since Turkey was not involved in the negotiations of the free trade agreements concluded by the EU with third countries over the last 20 years, these agreements have functioned to Turkey's detriment. Turkey cannot be a party to those free trade agreements, simply because it is not an EU member. So Turkey needs to sign bilateral deals with countries that conclude free trade agreements with the EU. However, these countries are generally not in favor of doing this, because they are Turkey's competitors in the market. As a result, a series of goods and services that enter the EU market without hindrance are being subject to a tax barrier when entering Turkey. The EU had imagined enlarging its market through the customs union, but this didn't happen in the end.
So problems involving the customs union were enough to put EU-Turkey relations into a crisis. To overcome this hurdle, a new idea has emerged: the customs union plus. It was a problem in itself, because we don't know why the EU is trying to develop a new form of customs union rather than speeding up the membership process? However, under the title of a so-called "positive agenda," even Turkey was willing to accept it. We say "was" because it never actually happened.
The customs union process has only created a "customs deviation" for Turkey, and in the meantime, there were attempts to block the membership talks with Turkey in order to impose a "privileged membership." This was a project aimed at keeping Turkey outside of Europe but close to it. So Turkey would have to accept the EU's rules, without getting much in return. It was mainly about expanding and deepening the customs union.
The privileged membership was about not letting Turkey in, but not pushing it away. The protagonists of this idea were saying: "as Turkey can never become a member of the EU, we must find a way to attach it to Europe with a different method."
Maybe from the EU's perspective, it was logical, they believed they found a solution to the "Turkey problem," but Turkey would not benefit from it. The membership process, which was already going on, was already a kind of privileged relationship, and no one in Europe was able to say why Turkey should accept such a "solution."
Let's recall that all these things were happening long before the July 15 coup attempt. Turkey was not being criticized that much for human rights issues or lack of freedom of expression back then. It was true, however, that Turkey wasn't doing all of its homework. The main problem at this point, however, was that the answer to one essential question had never been provided: When Turkey closes all negotiation chapters, when it adopts all EU rules, or economic, financial and commercial principles and practices of the EU market, it is still not be sure whether or not it will become an EU member. Why should Turkey work that hard, then, when it is not even sure that it will get into the EU?
The problems between the involved parties are not only at the political and human level. There are serious economic disputes, as well. We must admit, however, that political, humanitarian and legal cohesion are the basis of economic confidence.
The EU still hasn't made a clear cut decision about Turkey. Turks are therefore angry at the EU. The fact that they are angry means perhaps that they still value the EU membership process.