I repeat my old answer: Stake.
My suggestion is to hire a campaign manager, he's not capable to handle a campaign, he said that he will combat against AI usage and spams, but as we can see there's no improvement at all.
Other alternative is to replace all the existing posts reviewers, hire few users from this list.
1. Cut the number of participants you have in half, retaining only the highest-merited users with non-purchased accounts.
He will counter your suggestion by saying:
I dont really trust in the current Merit System, tbh. I have seen shitty posters with over 5k merits and I have also seen good posters that barely could reach Sr Member so no, dont ask me to use it as basis to accept or maintain members in the campaign because I wont.