FYI: Basically the way I think about U.S. equity market structure is:
".Real" investors (hedge funds, mutual funds, etc.) do not want to trade with high-frequency traders, because high-frequency traders are evil.
.Real investors do want to be able to buy and sell unlimited quantities of stock immediately.
.The only people who are consistently willing to trade instantly with real investors are high-frequency traders.
.You see the problem.
.The solution is for the real investors to trade on a platform that says it protects them from high-frequency traders, while also quietly having lots of high-frequency traders.
Regards,
Ted
https://www.bloomberg.com/view/articles/2018-04-18/investors-want-to-buy-a-lot-but-not-pay-a-lot