Granted that lens quality and aperture are key, but I still feel flash and specifically flash location are also important.
I see a distinct shadow over the arm of the person in the red shirt, and the back of the cat along the top and left side are also blurred and lack definition. The shadows are shifted slightly left of the subject, in the landscape mode for the shoot. This would indicate the flash fired from the right of the lens and thereby casting a left oriented shadow.
Knowing for sure exactly what orientation the camera was when you took that photo would help to identify the flash location, but I'm going with landscape - flipped 180 from the image above, and so the flash was on the right but slightly above the lens in that orientation. Given the flash is off-center from the lens to the right in the Y axis (as well as below), on the S5 while in portrait mode, it could be a combination of the flash being just above center line in the X axis of the lens in landscape, and to the right in this case. This would explain why the shadow appears more blatantly along the sloping of the arm and the left side of the cat's rear.
Careful staging of the photo, such as by flipping the phone 90 degrees to portrait upside down, so the flash would have been distinctly above and slightly to the left of the lens, instead of just slightly above and distinctly to the right of it would have eliminated that but for most phones with the flash on one side in portrait shots, that's not an option. For the flash being mounted below the lens as it is in yours, this presents a problem more-so in landscape as seen here, but in portrait shots there will be a distinct top shadow in those as well, unless the camera/phone is held upside down.
Yes, it's worse in the unedited photo, and the lack of definition is mostly cured in the "enhanced" image, but the shadow is still apparent in the edited one, and in the edited one there is slight over-saturation most obviously visible on the pink tablet case.
In the case of the flash location in the new Moto X 2015, I would have rather'd seen it above the lens for just that reason above. A top-mounted flash would have yielded a much better photo in portrait for sure, and even in landscape if oriented with flash to the left, before editing. If it were a dual-flash like the 2014 Moto X and Droid Turbo, there would be no shadows above the subject in landscape mode, since one flash would be effectively above the lens and the other below.
And yes, IMHO of course as well...