It is never too late to join bounty programs. But to get a significate amount of stakes in signature campaigns you need to have at least a full member rank, which is - at the current form of the merit system - nearly impossible to reach.
Yeah, this is correct. Specially for the shitposters and spammers. As we can see there's a merit system right now. If you post garbage content then probably you'll not be leveling up and getting higher rank and higher stakes for campaigns.