Let's look back further, with Satoshi Nakamoto contributions for bitcoin in particular and for crypto in general as well as his/her/ their dissapearance years ago.
I don't think there are someone who say that contributions of Satoshi Nakomoto is small, valueless, or devalued contributions over time due to growth of crypto recent years.
Just because someone is no longer active or as active as they used to be, doesn't mean their previous posts or contributions should be devalued.
Yes, I agree with your suggestion.
Simply depend on campaign managers, if they require strict rules for their participants, shitty users can not be qualified enough to apply and join.
I still think the neatest solution is simply to change the requirement for a signature to earned merit. No one would be deranked, inactive legendaries would get to keep their legendary status, but shitposters who had their signature grandfathered in would no longer be able to get paid for their shitposting.