What sectors have seen a depression of salaries as a direct result of Romanians entering the market? And you have the huge hurdle of proving that those salaries are depressed specifically because of the Romanian labor, and not because Asian products or other global trends.
Also - restricted migration fails to attract the right labor, driving up the cost of labor unnecessarily. Sometimes it gets ridiculously stupid... to the point that local consumers(also local labor) cannot afford to consume products, because local labor(also local consumers) refuses to work for less. It gets to a point where local businesses cannot pay their local labor and invest into productivity gains(required to keep the pay high enough).
It's a complex clusterfuck... and blaming Romanians or Mexicans is just an easy "solution".
After huge growth, the average salary in PPP terms is now about 50% of the Western ones. Romanian workers in the West have definitely depressed the average salaries in several fields.
And that's with somewhat controlled migration.
My point is: controlled migration is there for a reason. Building a working state is extremely difficult and takes a lot of time. It's a very fragile and delicate thing. Once you've managed to build it... you really don't want to upset the balance.