I noticed that I now sometimes write negative comments for poor/incorrect posts which in the past I would have merely ignored. At first I felt bad about doing so but was compelled nonetheless. On reflection I think it's a response to the number of low-effort/low-quality or factually devoid/incorrect stories that do sometimes make it to the front page.
I see value in a feedback mechanism for raising the bar of top voted submissions. Since posts aren't downvoted flagging is reserved for other use, what other acceptable means is there for providing this signal? At the same time, if there's not already discussion on such a post, even a negative one is engagement which could further popularize it.
Another thing I've started doing is being more liberal with my upvotes to get them above the floor of low-quality post scores.
Does this seem like what's happening and a fine way to approach it, or should something else or nothing be done?
Now, when to pass along a bit of feedback is a judgement call only you can make, but I think in most cases people will also learn by trying and failing.