Quite true, asylum is not granted, but it is still very difficult to send back those whose asylum application is rejected. Often it is not even clear where to send people "back" because they have no papers (human traffickers instruct them to destroy or hide passports) and no one can really tell where they came from.
The applicants have a right to appeal the decision; process takes years, then people make a new residence permit application based on "changed circumstances" (for instance, starting a family or having studied something) and more time passes.
This will be particularly flammable in cases where even hardened criminals cannot be deported because now that they are criminals, their home country (if known) definitely won't take them back.
And then the applicants may simply leave one country and emerge in another one as new applicants (unless biometric tracking is really started and made working).
I predict volatile times and violence for Europe.