Regretting buying this 14mm now that I got it

This is what scares many people away from playing around with the wide end. Also, over the years I have countless post from people blaming the lens for problems when it was a fundamental lack of understanding what is going on. What is going on is simply this, with a wide angle lens various parts of the subject can be much further away from the lens than other parts, sometimes 2 or 3x or more. This results in perspective distortion, twice as far means twice as small. It is the reason why you don't take portraits with wide angle lenses since to get a head shot you need to be so close that the nose might be significantly bigger than the ears. So the starting point for normal perspective for portraits is 50% greater than normal focal length - about 55mm for APS or 85mm for Full frame. The converse is also true, very long focal lengths compress perspective and for people the nose may appear in the same plane as the ears giving a flat look

The shot below inside St Patricks Cathedral in New York had exactly the same key-stoning issue and was corrected the same as above. Since the photographer is low the bottom of the pillars are closer to the camera than the top making them look small and therefore leaning away.

Perspective correction to fix the original keystoning