The difference between the two would be intent. The experienced filmmaker tried to do something for a specific reason, while the amatuer filmmaker didn't have the skill necessary to produce the film they envisioned. You said it should be obvious to me that you were "talking about movies made unskillfully, not directors or actors choices" implying that you make a clear distinction between the two.

The bottom line is film quality like as with all art is subjective. For every element in a movie whether unintended or intended, made by an experienced filmmaker or an amatuer, the final decision of whether it contributes positively or negatively to the quality of the film is purely a subjective one.