Scoring is what you want to minimise, correct. You do this by playing defense. Player 18 defended FAR better than player 8. You can't deny him a great performance cause he allowed 1 basket. He was under more pressure cause the player(s) he was defending took far more shots, so his defensive work load was far higher, and to allow only 1 basket from 17 attempts is amazing. 0-8 is great too, but it says that the defender had less work to do, although he did his work brilliantly as well.
Yes, there are only a limited number of possession in a game, 48 minutes worth to be exact. Around 80-90 possessions per team in the game, so yes, there's limited possessions. By jacking up more shots that don't hit, you're effectively reducing the number of scoring possessions your team has.