The Duncan era is so different from what it is now. With the first and second apron teams can no longer throw money at championships, which is great for a small market team like the spurs, but it also means that it will be extremely difficult to renew multiple max level players and keep a core together for a long period of time (duncan ginobili and Parker were max players).
The Second part is that the play style today is no longer as single player dependant as before, back then a top five player on your team would pretty much guarantee a playoff spot, right now with so much ball movement, switches and cuts you can no longer have any weaknesses at any point on offence or defence. The effectiveness of a player like Bowen would be limited and players like nesterovic, Nazr and such are pretty much unplayable. To build a team with continued success around a player like wemby in a small market the team must load up on picks to cycle through third option and supporting players year over year. We can have a second option locked up but financial management is the name of the game going forward.