As an IRON CLAD RULE, a may-God-smite-you-with-Araujo-if-you-disobey rule, you never -- let me bold that -- never, draft for or around position. You have 8 C's on the team and Drummond is the BPA? Guess who you're drafting...
It's one thing to say there were serious concerns about his ability to transition to the NBA (there was some credence to this given his college performance alone), it's another to package that with an argument from positional necessity to justify foregoing him for Ross.
And as long as we're making no-hindsight-aloud arguments -- it was common knowledge that the Pistons (as well as several other teams above us in the lottery) coveted Drummond. Even if you were going to swing him for Ross/Lamb immediately, the smart move was still to pick Drummond first and then either get an additional asset in the trade, or at a bare minimum, pay Ross in a lower salary bracket.
Reaching for anyone, Ross or otherwise, when such a highly coveted player was still on the board, was (and is proving to be more-so every day) a crippling moment in Raptors history.