It's a huge bummer for Cousins. If he could have bided his time for one more year, he likely would have gotten a sizeable offer in free agency 2020, because there just aren't that many top tier players in that free agent class.
It's looking less and less likely he ever makes another big NBA contract.
He was one of the biggest name players to take a serious paycut to play in a competitive environment. He will probably be a cautionary tale for vets thinking about the same thing. This could lead to more guys signing bigger contracts with worse teams, which could mean more competitive balance.