The flow of migrants has been largely reduced, but that doesn't stop the racist populist fringe from exploiting the issue for its own agenda. Basically, the instruments to reduce the flow are in place. Unfortunately, the polarized political debate hinders the intelligent management of migratory flows to the mutual benefit. The problem with nationalist populism is always that it damages the own nation in the end.
I live in a small village in one of the poorest parts of the Euro-zone. Ten years ago, we had never seen any Asians in our village. Today, there are an estimated 5,000 Asian guest workers from Thailand, Nepal, India, Bangladesh, etc., who are flown in two work in the surrounding farms because there are not enough locals willing to do hard manual labor. This country of 10 million has engaged to take in about 2,000 refugees, of which only about 700 have stayed. That number is insignificant if a small village can take in 5,000 guest workers from Asia without causing any social conflicts.
In Germany, despite of what Trump claims, crime rates have reached historic lows. Generally speaking, immigrants and refugees who have received permission to stay are on their best behavior with below average crime rates, while illegal immigrants from the Baltic or North Africa who have little hope of getting asylum have above average crime rates because without the means to work legally, they often live by crime or illegal activities. It is often difficult to deport immigrants whose asylum request has been turned down because of a lengthy legal process, lack of proper papers, or unwillingness of the countries of origin to take them back.
There is no doubt that the 2015 refugee crisis has left deep marks in the political landscape, but I think it was a good trial run that has prepared Europe for bigger migratory movements which are bound to hit the continent in the future due to increasing international inequality, climate change, etc. While I regret the rise of right-wing populism, it was a natural consequence of the inability of liberal-left politics to deal effectively with the refugee crisis. Thus, the rise of right-wing populism was a natural corrective in the EU democratic process which introduced a sense of reality into those who opposed all restrictions on immigration.
In Germany about 60% of the refugees from the Balkan wars in the 90s have returned. The rest has somehow put down roots in Germany. Once the situation in Syria stabilizes, it is expected that most Syrians will return. The problem is that the West has backed the wrong horse in Syria and even though Putin has asked Merkel to help rebuilding the country, having backed the wrong side, it is now hard to do a U-turn for creating the conditions that would allow the Syrian refugees to return.
Edit: It should be noted that the percentage of foreign born citizens in Europe is still below that of the US and that the perceived percentage of foreigners in a country is well below the real percentage:
Where Europe’s migrants are