About the OP, I know what you mean, there are different kind of managers and preferences on picking a participant of a signature campaign. So we don't have a choice to accept that some of them are gaining income even they're not good at posting. So it's a matter of chance on being a campaign, it's not a big deal in here so we shouldn't care about them. Let the campaign managers handle that thing.
Ranks have an important goal, the real thing about ranks is how we will interact with other people by having a high rank. If they respect you every discussion you'll engage, then you've done a good thing being a respectable member of this forum. If not, then maybe you've done something that the others don't want to see, or you've disrespected someone.
I also have a suggestion for you, report them if you find their posts as low-quality.

Some things managers likely consider when screening applicants to choose participants:
- Post history to check post quality
- Trust Flag history
- Language: mixture between English and local; or purely English
- Average posts per day/ week
- Inactive or active posting in recent weeks
since merits are hard to acquired, so assuming that managers are also looking for people that contains merits.
Merits should be included there, most of the managers are looking for merits because it serves as proof that you've done quality posts or something good in this forum.