We know you hate data and metrics and fact in this discussion and only want to focus on your 'Feels' but your feels are wrong.
If you took a second to try and understand why the Springfield, year over year population data, could not be allowed to continue on that trend line, then you would have to accept that the jobs you think the immigrants are degrading are actually being SAVED by them. Those jobs are all going away otherwise.
At a much bigger scale this is the same issue many countries, CHina chief amongst them, is having with an aging population and not enough young workers to coming in behind them. It is a problem in the US and many other countries to a lesser degree.
Would China, bringing in a bunch of young Indonesian or Indian workers who are even poorer, to help fill jobs, and to stay and live in CHina help fix the problem? Yes... Yes it would. But because China is also xenophobic, as you seem to be struggling with but not admitting, they will instead face a massive crash.
The US became the wealthiest country in the world for the exact reason you claim makes them fail. By taking in, from each country across Europe, mostly the lowest paid, desperate workers and allowing them to help grow the economy. At each and every arrival of the new immigrants (Russian, Italian, Irish, Roma, Jews, etc) there were people like you repeating the EXACT same arguments you do. EXACTLY THE SAME.
And despite the undenyable proof of the success, growth and wealth it spawns, each and every generation, people like you claim the opposite.
You are not unique. YOu do not have any special insights. You have very old and proven wrong xenophobia based beliefs.