Read what I wrote again. It's about payment for order flow. The hundreds of millions of dollars they are paying to brokers.
A seat on the NYSE isn't even a significant fraction of what Citadel pays for order flow.
The rest of your argument seems to degenerate into "well other people have paid for special market position before, so it's good that middle men are getting in between". That's not even really an argument.
PFOF is awesome.
It keeps your commissions down and you are put into a bucket of dumb traders. If you are a reasonably smart trader this provides liquidity to you that you wouldn’t have.
Trading against people who think you are smart, when you are actually smart, is really hard.