I don't think it's fair to put this on either the EU or Turkey alone. There were many factors prevent Turkish membership but the parent is right: religion played a huge role in the public opinion.

I remember Merkel actually saying that Europe was founded on "Christian ideals" (nevermind the actual ideals having more to do with post-renaissance secularism than original Christian dogma) -- the same Merkel nationalists are now blaming for the "Islamification" of Europe.

If Turkey had been more compatible and the EU members had been less bigoted, I imagine Turkey could have even helped with the "Islamification" so many people are now worrying about -- it would created a European example for how Islam can work under Western ideals and prevented a lot of the guilt and xenophobia that lies at the root of a lot of the conflicts with Islam we now have in Europe.