If a train is so crowded that you really have no choice but to stand right in front of the door, and you’re not exiting at the next stop, go ahead and step off the train at that stop, then stand on the platform just to the side of the door so the doorway is clear for exiting passengers. When the doorway is completely clear, 2 passengers can enter/exit at a time. When someone is standing in front of the door, it’s only one.