At what point in the history of the public markets in the United States was market-making of any sort not an activity reserved for an incredibly small minority?
The difference, from what I can tell, between the HFT "elite" and the human market-maker "elite" is that the human elite actively colluded to retain their status. Compare the largest HFT firms to the largest investment bank, and the number of entrances and exits in the market for electronic trading firs.
There are market makers, and there are Market Makers. In practice, the registration may simply be a formalization of an existing trading system, or a very light obligation on top of the existing system.
From the document that you listed, it looks like NYSE Arca has a requirement for 100% continuous quoting, but the quotes can be 8% away from the current market price (section 7.23.a.1). This is basically a free pass; nobody wants to trade against a quote that wide. For reference, take the most liquid ETF: SPY trades above $150 and regularly has a $0.02 spread, one THOUSAND times tighter than the 8% requirement.
On other exchanges, there are requirements for tight quotes, but they usually come with relaxed requirements on quoted time. For instance, maybe a market maker could be required to quote "90% of the time within a 0.5% spread". In such a scenario, allowing market makers to pull quotes for 10% of the day is basically giving them a free pass on the most volatile points of a day.
I have seen very few situations where registered/designated Market Makers are obligated to suicide themselves to provide liquidity; there's usually an "out". In practice, the top-tier HFT market makers (de-facto) are already exceeding the obligations required of Market Makers (registered).
The difference, from what I can tell, between the HFT "elite" and the human market-maker "elite" is that the human elite actively colluded to retain their status. Compare the largest HFT firms to the largest investment bank, and the number of entrances and exits in the market for electronic trading firs.