In reality the way that markets are cleared wasn't necessarily so much more different than a turn-based one, even in one where the clearing happens by the minut

In reality the way that markets are cleared wasn't necessarily so much more different than a turn-based one, even in one where the clearing happens by the minute. The issue is, indeed, mostly with HFT. However, you shouldn't consider HFTs to be market participants in the traditional sense. Most of them focus solely on moving stuff around very fast instead of actually trying to purchase or sell things for a separate economic goal (e.g. production, hedging, short- and long-term investments). Once you disregard the rapid transactions that do not have a significant effect on the price, your average human investor is probably putting down some fill-or-kills or limit orders and actually benefits from HF liquidity trading. It's hard for me to understand, let alone explain, why milliseconds would matter for the human investor, but I what I can tell you is that GS is not investing 100M USD just for buying derivatives every other minute.