Holdo sacrificed her life by ramming the First Order capital ship with the Raddus (using the light-speed trick),
why didn't she use auto-pilot? Or use a droid?
By the time she decided to use The Raddus in a hyperspace kamikaze attack, the Resistance transports were already being wiped out. There would not have been time to set the auto-pilot and escape before more (perhaps all) of the transports were destroyed.
Before sacrificing herself, the point of staying behind was to ensure the First Order was distracted by the larger ship. The First Order might have noticed that the ship was on auto-pilot, but with a human pilot at the helm, she can navigate, make turns, and otherwise convince the First Order that The Resistance was still on board.
There were no transports left.
By the time the First Order stopped firing on the The Raddus and started destroying the smaller transports, there were no other transports aboard the cruiser because they had already been evacuated.
Maybe autopilots don't exist?
I say this because I'm pretty sure I recall a debate on the First Order bridge where someone says that there's no point paying attention to The Raddus because "there's only one person on board". How could they know that, if autopilots are a possibility (in universe)?