I had doors that started getting very stubborn to open from the outside handles. When I disassembled them I saw that the rods going from the handle was bowed and wasn't pushing straight up & down on the latch, it was also pushing "across" the latch lever. This could also happen to the interior door latch rod. Make sure the handle to latch rods are operating in the right direction, and easily snap into the clips easily. If you have to really tweak the rods to put them back in the latch, you might want to take them out and straighten them up.
If your doors aren't aligned properly, and are riding up or down on the striker post when the door opens & closes, you'd want to fix that. This could happen due to rust or an accident. My truck was rolled by the PO & it wasn't put back together straight & square, so I had to do a lot to get my doors to open & close right. Left unrepaired, you'll damage the door where the latch screws, and other things. Any compliant bodyshop can address these things. But be prepared to hear bad news. My doors don't line up with the fenders, but open & close nicely. Function is more important to me than fashion.
Chad