I don’t think his legacy as a great NBA player is tampered but it will definitely be “complex” and that’s putting it mildly. Durant didn’t ruin the league or insult players around him. Warriors presented him the best deal to win a title and establish fame with no real long term consequences. Anyone would have said yes.
Warriors built the team the right way and signed free agents based on their skill sets beneficial to the team. Durant is no different except he’s one of the best players in the league. It’s like the case of the NY Yankees in baseball. They build the team the right way and seek the best free agents that help sustain long term success. It is what it is.