Unfortunately this cannot be changed to a decentralized system. The abuse has always existed. It would only be possible to block such accounts. But maybe Steemit inc. should go the way and really block such accounts. Only that the reward + curation part is sent to zero. That would do it. Freezing the assets on the account would not go over well.

Unfortunately, Steemcleaners also abused the system and they had only enriched themselves with comments by voting for them.