While I 100% agree that Walton is a terrible coach, there has to be some point where a superstar is a superstar independent of the coach right? Putting aside Fox just so we can discuss this more objectively - take Cousins for example - while he wasn't considered a winner, he was considered top 3-4 big men in the NBA, made the all star team etc. Likewise with KAT - he was at one point considered a top 3 franchise cornerstone in the league, despite not being a winner, and then started losing his shine.
I think that coaching has a lot bigger impact on role players than it does on star players as far as personal reputation goes, or on guys you wouldn't have expected to be stars becoming stars. To say "you have to have proper usage before deciding anything" sounds pretty subjective/circular to me. It's like saying "you can't decide whether a player is a star until they play like a star".