Tim Duncan was drafted in 1997. The Spurs landing Duncan in 97 has little to do with their finals appearance in 2013. To argue that the only way we can land a player comparable to 37 year old Tim Duncan who plays 28 minutes a game is by tanking is nonsense.
Nonsense?
In fact, it makes perfect literal sense.
Tim Duncan was drafted in 1997. He has never since entered free agency or given any indication of his intention to play for any team other than the Spurs. The Spurs, for their part, have always re-signed him with enthusiasm and have never shown any interest in trading him.
So yeah, if you wanted to get Tim Duncan this past season, you needed to draft him in 1997. Tim Duncan was, at age 37, the most important player on a team that came within a hair's breadth of winning an NBA title against a superstar-laden juggernaut.
Indeed, the Spurs drafting Duncan in 1997 had a TON to do with them making the Finals in 2013. They had to make a lot of other really smart moves in between, but Tim Duncan is the one factor that made it possible. The only other factor that comes close in importance is their coach, Greg Popovich.
Now, I get that your point is that you don't HAVE to draft a guy like Tim Duncan to get a Hall of Famer who is on the tail end of his prime, or just plain in decline. That's technically true. After all, the Celtics took advantage of a set of circumstances that made Kevin Garnett available for trade.
Still, Tim Duncan is on a different level than even Garnett. And even at age 37, Tim Duncan was one of the very best players in the league. Guys like that are never available in a trade. When they're available in free agency, they join the Lakers or the Heat.