Not an optical illusion or a problem with the camera ... because of the way adobe walls are constructed, they have an obvious slant. The doors are typically installed to match the lean of the wall, using half-mortise hinges and rim-mount locks.

You can regard it as convenient - it gives you self-closing doors if the door is installed leaning inward. Or you can drive yourself nuts trying to make everything all square and vertical and gringo-style.

The doorway in the foreground has its own lean, but it's leaning away from the camera so it's not obvious.