I'm the one who declined the flag.
First of all, thanks for your efforts to help keep the site clean! Keep flagging, don't let the decline discourage you.
Since you've opened a discussion here, I'll try to give you some insight into my thinking. I always fear that the moderator responses (especially standard ones, as I chose for this flag) don't really offer a full explanation for a moderator's thinking, so thanks for bringing it up here since you had a concern.
Per the flag response "flags should only be used to make moderators aware of content that requires their intervention" (which is one of the standard response options), the only action that a moderator can take is to delete an answer.
You're absolutely right, we do want to cut down on repetitive and unhelpful answers. I think the best action we can take is preventative, and when that doesn't work, downvotes are our second best tools.
Deletes should generally be reserved for things that are not an answer to the question (completely off topic, spam, etc.) or simple comments or questions (see, for example, my comment here — the user revised and expanded their answer after my comment, which was the best outcome for all).
The answer that you flagged:
- Has a positive score, no down votes.
- Is actually an answer.
It may be a bit ranty, or may draw the same conclusions as another answer, but it is in fact an answer. In this case, if you think it is a bad answer, I think your best tool is to use your downvotes (I do! :))
Unless an answer actually repeats another answer (not just draws the same conclusion), I would be against using the delete tool to deal with it (as a moderator or high-rep user).
As always, moderation of this site is a discussion and we're all learning. I welcome any feedback you have for me, and I hope this helps!