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.
How did Player 18 defend far better than Player 8? Player 8 defended perfectly because no shots were made. Player 18 defended almost perfectly because 1 shot was made out of 17. I am not denying that 1-17 is a fantastic performace, I'm just saying that the scoreline at the end of the game doesn't take into account prevented shots, it only takes in to account shots that were failed to be prevented. If player A kept his opponent to 0-20, and Player B kept his opponent to 4-50, then whilst player B was very impressive in his defence, he still allowed the opponent to increase their score, where as Player A was able to succesfully prevent every attempt and thus prevented any scoring.
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.
I agree that the time is limited, but I disagree that there is a limited number of possessions in the game (at least no identifiable number). If you think there are (hypothetically) 100 possessions per team each game, then I agree with you that the 1-17 is better because they are wasting an additional 9 possessions, however, I do not believe this to be the case. I do not think there is a set number of possessions per team per game, and thus wasted possessions are irrelevant, and only the result of scoring or not scoring from such possessions ought to be considered.