Productivity is the root of all prosperity. First read this excellent article: http://econlog.econlib.org/archives/2015/02/always_keep_you..... Workers become on average ~20x more productive when they migrate to the first world. Because we are capital rich and we have sane government and law and order. Imagine if you were moved to Haiti and you got stuck there. How much could you contribute to society in Haiti? You could maybe slice some coconuts on the side of the road - is that gonna make the world a lot richer? Roadside sliced coconuts? Nah, much better for you to be in first world even if you're doing a low skilled job here like delivering catering to a high tech startup. That catering company is able to produce food much more efficiently, and in SF or NYC you're able to distribute it much more efficiently, and you're part of this souped-up economic engine that's changing the world. That's why they make 20x or up to 40x more (in the case of the extreme poor) when they migrate to the first world. It's better for everyone! Economists estimate that moving from the status quo to fully liberalized migration (i.e. open borders) would roughly double global gdp - that's an insane silver bullet. That's everyone getting way fucking richer in one fell swoop.
You make the all too common mistake of confusing aggregate output growth with everyone getting richer. That's not a valid equivalence, as the 2001-2009 economic expansion in the US showed fairly dramatically, with the bottom three quintiles doing worse over the period of expansion, the fourth quintile mostly flat, and most of the gains in the to quintile (and, within that quintile, mostly in the top few percentiles.)
Aggregate growth doesn't mean everyone gets more; we have a system in which the major holders of capital are very good at capturing output growth.
Policies favoring aggregate growth aren't good for most people without policy reform that alters the way gains from such growth end up being distributed.
Please see my comment here for more info: https://news.ycombinator.com/item?id=9769632