First check for wear in the door hinge pins, if they are OK, you could try this:
This is going to sound "Brutal" and a bit drastic, but I've done it a few times, and it has worked for me.orks.
Open the door slightly, grip the bottom rear corner, and heave upwards.
Start gently, and increase force gradually if necessary, you may have to do this a few times. It shouldn't damage any new paint, but the result is usually pretty impressive.
Nothing is foolproof to a sufficiently talented fool