Pavlov. totally agree - there is so much junk that spams the bandwidth and swallows quality posts.
Downvoting is fine, if you have a decent rep - as you do. Anyone below that - it's risky.
Don't ever downvote someone with a rep higher than yourself - as it will not affect their rep, but a downvote from them will impact one's own rep.
I am starting with going critically through my feed and unsubscribe to all many who have not engaged once, particularly where I commented on their posts.
Use the MUTE feature - I haven't yet - but it is there for the taking.
As my reps are still baby minnow territory - I focus on positive re-enforcement.
But right on - I am all for moving usurpers to the forgotten corners of Steemit from where they can ponder what quality content means.
It really is Steem Power rather than the reputation that gives weight to flags. But as you said we should get rid of bad quality content so new users can excel.