Earlier quoted context omitted.
If what you are doing requires registering with the SEC for it to be legal, and there's no way to register what you are doing with the SEC, then that means that it is illegal to do what you are doing (like how could you think that possibly means you are free to go do that thing?).
If there is no way to register with the SEC to run a securities brokerage, exchange, and clearing house, then what's the point of the SEC again?
As a result, the SEC does not allow anyone to run an exchange that trades those illegal securities.
Being a registered security isn't hard, all sorts of stupid and speculative instruments get registered. If your shitcoin isn't able to get registered, the fault is with it, not the SEC. If your exchange isn't allowed to trade that shitcoin, the fault is with the coin, not the SEC. It's not the SEC's job to provide guidance on how to run an exchange that trades in unregistered securities. The only guidance it should provide in answer to that query is 'You can't.'