I'm surprised Fidelity is still doing this. But I've found a bit of a workaround. They let you put in at least a couple orders on what they deem to be a low liquidity stock (many microcaps unfortunately). Then the restriction message starts showing up. But if you wait like 30-40 minutes, you can put in some more orders. Not much help if there's breaking news and you want to buy/sell a bunch of stock quickly, but it's something.