The difference is you are only looking at an individual player's talents. You then use these individual talents to compare against another team's individual talents. As previously discussed, such a comparison doesn't translate to the court. Luckily there are metrics in place which can help people determine which starting lineups play well as a group both on offense and defense. As with any metric, one should determine what other factors to consider, such as strength of schedule. But these metrics are a much, much better starting point than simply using the "eye ball" test, and it's far better than trying to compare individuals between teams. It's a team sport after all