This has always been a problem, due in part to the Not An Answer (NAA) flag previously having some unclear wording, but Not an answer flags are not intended to be used on low-quality or wrong answers. This has been brought up before, but since the NAA continues to be used not as intended I think some clarification is required.
The description of the NAA flag is:
Not An Answer
This was posted as an answer, but it does not attempt to answer the question. It should possibly be an edit, a comment, another question, or deleted altogether.
The key things to note here is that it says it is an attempt to answer the question, and that it makes no mention of quality. That's because the flag is not intended to be used on wrong or low-quality answers, but posts which make no attempt to answer the question at all. This includes posts like "Thanks!", "I have a similar problem!", and "I'm not sure what advice to give you, but that boss was so much fun!". None of these attempt to answer the question, and should therefore be flagged (and deleted) as Not an Answer.
When the flag shouldn't be used is when users attempt to answer the question, but their answer is either wrong or of very-low quality. This includes answers which don't cite any sources, or are just guesses. They're not good answers, but they're still answers. For these types of answers you should downvote, not flag. Leaving a comment explaining what's wrong can be a good idea too, but not always (and if you do, be nice. "This is crap" isn't a helpful comment). This actually isn't all that different from how A Close Vote is not a Super-Downvote. Please don't use it as one.