I don't even understand why Duncan wouldn't be a top 10 player in the league.
He was one of the best help defenders in the league history, he was, at worst, had the third best low post game in the history of the league (behind Hakeem and McHale), he evolved into a fantastic low post passer, he did the dirty work, he was the floor leader and anchor for the Spurs on both offense and defense for championship teams, he won the championship with 4 (some can argue 5) very different iterations of the Spurs (1999, 2003, 2005 and 2007, 2014).
Duncan is easily one of the top 10 of all time.
In terms of building a team, Duncan is even better, as the article stated. Jordan wasn't particularly great to build a team around. He was ball dominant, he requires a bunch of bigs who can do the dirty work inside (defend, grab rebounds) and can shoot a decent mid range jumper, and those players are not easy to find, he requires another ball handler to allow him to post up during the later stretches of his career. He was absolutely dominant in his game, and can impose his will on his opponents, but there are ways to beat Jordan while allowing him to go off if he didn't have the right teammates. Duncan on the other hand, adapts his game depending on the players around him, maximizing their strengths so that the team can compete year after year.