"you need younger, more dynamic people inside of our economy..."
And the current flood of illegal immigrants are not noted for being the “younger, more dynamic people” who can be counted upon to grow our economy.
The illegals come with an attitude, and no inkling of what it takes to become a real asset to what has always been described as “the American dream”.
They bring their barrios and mindsets and social unrest with themselves, unable to shed them at the border, of no value to this country and probably of little value even in their land of origin. Only scantily educated even in their native language, and with no wish or intention of EVER integrating with the wider American culture, the only thing they bring is a warm body, probably great for population counts, but far from being a zero-sum game, they create a negative in the averages of skills, wealth, and enterprise.