In the past 20 years one team has won the NBA championship with arguably a point guard as it's best player (2004 Pistons.. and they break almost every rule) meanwhile the Rockets, Spurs, 3 peat Lakers, Celtics and Mavs won because their best player was a C/PF. The repeat Lakers second best player was Pau Gasol, 06 Heat had Shaq and the later three Peat Bulls had hall of famer Dennis Rodman at the 4. Bigs are your building blocks, and everything else should be on the table to move for All NBA calibre bigs.
Your building blocks if you want to win titles over the last 20 years have been Kobe, Wade, MJ, Shaq, TD and Hakeem. Back it up another 6-8 years and you add Isiah, Magic and Bird. *Those* are your building blocks. Look at your "essential" players that weren't the best player on your team: Rodman, Gasol and a late career Shaq. You can go all out to acquire a player like that and build around them until they retire, clone them and build around them again and you get nothing. The titles came not from those players but from MJ, Kobe and Wade.
Your "essential" list also contained Dirk and KG. Minny tried to build around KG for most of his career with no luck. And Dirk? Haha. Those Rockets teams from when MJ was retired would be the only title teams since the 70s the Mavs might be able to beat, and it's the first title of a, what, 13 year career? Right place right time, no more.
By the way, Dirk's a pretty good illustration of how silly this is. The reason you need a good big on your team is for strong interior defense, tough rebounding and a low post scorer on offense. Dirk gives you none of these. As a player, he doesn't have much more in common with Hakeem or TD or Shaq than Pierce or Rondo.