The September that never ends. This has been a problem in the internet since its initial days (in the Usenet for example). The problem with systems like Reddit (less so news.ycombinator) is that the "ethernal september" cultural shift gets amplified by content voting. Given that the masses have equal right to vote content, the "minimum common denominator" is the pattern that arises in the system.
Sites like Slashdot or news.ycombinator try to work around this by giving voting powers to certain "filtered" populations (Slashdot algorithm was actually nice when I read about it). But I feel the current approaches serve to "delay" the inevitable path towards low-effort content, instead of cutting it from the beginning.
The one thing that was nice about usenet is that all comments were equal, so there was no "amplification" of the low-effort content. I think for people to provide higher effort content, there should be some kind of incentive. Social incentives is what StackOverflow or Quora used to have, as well as Slashdot at certain level (you knew you were in a conversation with highly technical individuals). I also think that using real names would help.