People care way too much. Brokers used to take huge commissions, now the HFT market makers really aren't as exploitative as people's imaginations believe. Virtu is a good example, its a $3B market cap, less than half the size of Twilio.
I agree with this, as an individual investor, from my perspective the most likely thing that happens is that the SEC screws things up.
I started out paying what in today's money would be $50 a trade to buy or sell a stock. So for a $2000 trade, that's going to mean starting out down 5% on trading costs ($50 buy + $50 sell). Now I pay nothing.
Does it matter if I pay $50.01 or $50.005 per share on a trade? No, it does not. Leave it alone and let the brokerages compete, they're not monopolies. I much prefer the current system to even a small risk of having to go back to commissions.