I suppose the difference between McLemore and Durant/Curry then becomes that he doesn't offer anything other than shooting at this point of his career. FG% aside, both Durant and Curry are far more capable creators off the dribble and that means they can get to the rim when their shot isn't falling or set guys up off of penetration. Therein lies the problem.
Also, just looking at the general concensus here it seems that many feel McLemore will suddenly become open in the regular season just because we have Cousins (the defense is NOT going to plan their schemes around stopping Vasquez/JT/Ppat/Landry/Luc/Salmons). If I'm facing the Kings I'm getting one guy to just stick to McLemore, very much like what the Heat did to Danny Green in game 6/7 and what we should have done with guys like Korver and Ryan Andersen. Now if you want to free Ben up it's going to take a lot of off-ball movement frmo both him and his team mates in setting screens for him and such. Seems like a lot of effort to get your #2 option on the board if you ask me ... He will have to get better at creating for himself if he's ever going to be in an all-star discussion.