If the US didn't pay 3-4x the salary for software engineers compared to Canada, I wouldn't be here either. If China paid me more, I'd move in a heartbeat.
This comment encapsulates in a very crisp way why people are skeptical of immigration free-for-alls. Many feel the same way you do, that it's just a method of economic extraction and they don't have any skin in the game for the long term health and viability of the host Country.
Because there is no such thing as a "global citizen", first of all. And just taking a look around, the death of the nation state must've been greatly exaggerated in some circles.
>these experts are most likely paying taxes at the top tax bracket.
Who cares. This is a thinly veiled attempt to say that any person's worth in a given society is approximately equal to how much they pay in taxes - which is insane, for a great many reasons.