Actual membership for Turkey hasn’t been a serious option for a long time. Turkey knows it, EU knows it. There simply is no other label than “candidate” that could better describe what TR means to the EU. They want to keep it as close as possible, and TR benefits from it, a lot. A symbiosis, if you will. As for the Switzerland model, the EU clearly stated, multiple times, that they don’t want to repeat the unholy mess of relations they created with CH and, in fact, would rather transform it to something in line with stock EU foreign policy.