Why can't these ships be fully autonomous by now, or at the very least, remotely disabled and piloted in such emergencies??

Outside of short coastal routes, the notion of autonomous merchant vessels is so silly. While there is maybe a little more opportunity to automate some watch standing duties, autonomous systems (including sensors) are not even remotely capable of safely navigating a ship in congested waters. You still need guys looking out the windows with binoculars and talking to other vessels on the radio.

Plus on a ship everything is constantly corroding and breaking. If nothing else you need trained crew on board to do preventive maintenance and repair. When a ship loses power in some remote area it's tough to bring in technicians before the ship ends up on the rocks.