good rebounder. One has to be a lock-down perimeter defender on opposing guards. One or two have to be good shooters from distance. One needs to be a good ball-handler that can initiate the offense and help the PG. One needs to be a shot creator and/or draw fouls.
Nobody is rolling out three 6'2" guys at those wing positions. I guess if every team can land three 6'9" Kevin Durants, then all those problems are solved, but that fantasy hasn't become reality yet.