I did not have the impression that it has gotten worse recently, but it's hard to know. I take your opinion seriously, though. I'd appreciate your help in identifying posts that are "[gaming] by social marketing teams, journalists who work for re-spamming blogs, and growth hackers". It's my job, and my fervent desire, to make the front page inhospitable to such dreck.
HN has been in an arms race for a long time against artificially promoted content, and we (mostly PG) have developed a lot of defenses against it over the years--a large part of why HN is still standing. I've written software to combat such gaming and I intend to write more. One thing I'm pretty sure of, though, is that the problem of bad stories is easier than the problem of bad comments, and it is the latter that poses the greater risk to HN just now.
Incidentally, this past week was a good one for the HN front page. These two threads, in particular, were IMO as good as any in recent memory: