They, along with others still in line feel cheated by the people entering illegally / abusing the asylum claim systems. If you're escaping a bad situation in a central or southern American country, and then pass through 4-5 countries to get here, you're not seeking asylum, you're an economic migrant no different from immigrants from India, China, etc all seeking a better life.
No other developed country would or should allow people to illegally enter and skip the legal process.
Perhaps the situation in the UE since 2015 did not reach you. Google "Wir scaffen das!"
The minute you announce some kind of concession for people already here (which would most definitely be part of a broader immigration reform bill) then the floodgates will open with people trying to make it in before the effective date.
[1] https://www.cbp.gov/newsroom/stats/southwest-land-border-enc...
Either way, I can’t see any progress on immigration reform. It’s not happening, unless the flow at the border stops or reduces significantly.
The idea that immigrants are a net cost in terms of social services is nonsense.