Google/Facebook have displaced other ad formats, redirecting money to themselves. AWS have displaced IT technicians in other corporations, redirecting money to themselves. Apple is selling overpriced commodity hardware, redirecting money to themselves. Uber is displacing taxis, redirecting money to themselves.
In other words, it's barely above zero-sum game. And US productivity statistics are clear - the aforementioned corporations grew 500%-1000% in their profits and valuations since 2010. Meanwhile, the US productivity has grown by 4.7%. Had the SV tech been a clear net positive to the economy, the productivity growth would look different. When the tech/telecom was truly creating new value (1995-2005), the productivity growth was at 27% that decade.
(1) with notable exceptions: Microsoft really is creating value where one didn't exist before. So is Netflix, Amazon's venerable logistics and Tesla's drive to decrease battery costs