I'd argue that a robust and liquid financial market does "create wealth" in that it opens up new strategies that were previously too costly. For example, due to lower spreads, automated pricing, and decreased transaction costs, it is now cheaper than ever before to rebalance one's portfolio frequently to avoid over-exposure to certain sectors, gain exposure to more diversified international markets through ETFs, etc. etc.

A lot of this even has ties to the real physical economy. With a tight liquid market on the screen, commodity producers/consumers can adjust their oil/grain/gas hedges in real-time, retailers can manage their foreign exchange exposures and make live adjustments as orders arrive, and so on. Just makes the economy more efficient and reduces "slop" where end users built up risk exposures they didn't really want because hedging it was so expensive.

And I agree the HFT is creating value, especially market-making HFT. Absent his bid or offer, you would either lose more money paying a higher spread, or lose more in opportunity cost wasting time to wait for another trader on the other side. People who trade with them "lose" like people buying insurance "lose." Not everyone has the same utility function.