That year the Suns expected to be bad and won 48 games and missed the playoffs by one game really messed them up pretty badly.
Kind of? They got TJ Warren in the draft that year at pick 14, who’s turned out better than about half of the picks ahead of him. The next year they got Booker at pick 13 as a near-.500 team, so trying to win that year and failing at it didn’t set them back too much either.
The mistake was how they reacted to that season in free agency. With Dragic coming off an All-NBA season and Bledsoe in restricted free agency and not getting offers, they signed IT. While this was a fine signing in its own right based on production and value, it created three point guards on the roster who all needed the ball, thus making it a poor fit on offense and an even worse fit on defense. This created a rift that resulted in both IT and Dragic being traded for picks 1-5 drafts in the future.
Even that would have been okay, but they also decided to trade the valuable LA pick for Brandon Knight, who again was a poor fit with Bledsoe. Because they had paid such a highly trade price for him, they then gave him way too much money in free agency. And to top it off, despite having a relatively young team, they signed a very old Tyson Chandler to a very long deal. This both wasted money and blocked their former top-5 pick center Alex Len from getting playing time entering his third season.
It wasn’t the winning so much as their reaction to it that messed them up.