Total BS. I'm a big fan of limit orders (though most of my purchases are DCA). Since Robinhood can't do limit orders (or couldn't when I was using it—or I couldn't figure it out), it's useless.
You can do limit orders now! The interface is still kind of clunky, but it works well enough for my use case. Still, I haven't used Robinhood for anything but short term speculation, as a toy.