Without that efficiency it'd be like the old days before electronic trading where you're paying 100x larger fees to a crusty old brokerage any time you want to trade.

Doesn't matter. Banning short term trading will also reduce # trade events, so the fees don't matter.

Why would the fees be bigger? The old brokerages had to do manual work to put the bid on the trading floor.

Electronic trading doesn't need to go away. The trade itself might take some time instead of being functionally instant, but that's fine.