I certainly value defense, which is why I'm so optimistic about Smart. But what is special about 45/35/75? In today's game those numbers, especially the 35% from 3-pt, are not all that good.
Whether his shooting has gone down "just slightly" or not, they've still gone down. He became a starter in 2011-2012 when he averaged 34.8 minutes/game. During that season he averaged 16.4ppg on 48.8 fg% and 36.5 3pt%. Now in 2014-2015 he is averaging 16.9ppg on 44.7 fg% and 36.0 3pt%. That's a 4.1 fg% drop, which is more than just slightly in my opinion. But most of all, his scoring has been trending downward. I still stand by my opinion that I don't want to trade valuable assets for a player who is at best not improving.
Not saying it's special on it's own. He's no Steph Curry, no doubt. However, I don't think there are more than 10 point guards in the league with his combination of scoring, passing and defense. Look at any of the past 5 seasons and see how many points guards have averaged 15 points and 8 assists in a season. It's usually 3-4 guys and not all of them repeated. Maybe another 3-4 guys who score a lot more like a Curry or Westbrook. So offensively, he's at worst maybe top 8-10.
Obviously you don't have to love him or trade for him (it ALWAYS depends on the cost), but you're cherry picking numbers to say he's on the decline. You can't cite slightly lower shooting percentages and then ignore going from 6.6 assists to 10.1, all the while shooting 50% more free throws, turning the ball over less, and posting a career-high PER with defenses keying on him for a lousy Denver team.