I do agree with these things, and I'd be a hypocritical liar if I said I wasn't motivated to post more because of the sig campaigns I've been in.  On the other hand, I usually end up posting over the maximum # of posts I get paid for in a week, sometimes waaay over.

The thing is, it's possible to be an extremely active poster and still not have your posts be spammy.  I'd like to think my posts are an example of this, and in fact Chipmixer's campaign is full of people who are prolific writers who don't produce a mountain of shitposts.

It's the crap like this:
which TheGodson has correctly identified as the problem with campaigns.  Campaigns have drawn in innumerable participants from places where English isn't spoken, and they're required to post in English.  The result is that while their desperation drives them to join, it's not matched by skill with the written word, and they resort to writing cookie-cutter nonsense like the above.  Or even worse, they plagiarize somebody else's posts or articles from the internet.

So if campaigns were driving really talented writers to post, that would be a great thing indeed.  Unfortunately that's not what we're seeing at all.  We're seeing the worst writers who are trying to earn the most money, and it's their posts we see most frequently.