I don't think the forum's quality has gotten worse over time, I just think the more veteran users have forgotten what it was like many years ago, but because of the constant issues have grown tired of it eventually.
The thing is that people tend to look at the past through rose-tinted glasses, often focusing on good memories and blocking the negative ones and same thing happens on this forum. I haven't been here long enough that I can talk about "good ol' times" but I've been on some other forums for ~20 years and I am definitely guilty of that when I look at the past. Then again, it makes sense to remember good stuff from the past better as we were younger, and on top of that its a kind of defense mechanism since dwelling on bad stuff ain't healthy at all.
You'll rarely see users participating in Bitcoin signature campaigns without actually being a decent poster
I kinda disagree with that. Situation was maybe like that ~2 years ago (I remember very good members fighting to get into lowest paid Bitcoin signature campaigns) due low amount of sig campaigns but situation now is completely different and it's a sellers market. There are way more spots in Bitcoin signature campaigns than there are decent members interested, resulting in managers lowering the bar as they have fill up the campaign.