This year NBA Elite 11 introduces a singleplayer "Become Legendary" career mode. The crux of your advancement seems to be outperforming the best player on opposing teams, according to this video examining the mode's matchups.
Experience points will be on the line in these games - to be earned or taken away, depending on how well or how poorly you do. Get schooled by a lesser player and you'll see the XP decrease; take down your designated matchup foe - do better than him, statistically speaking, while your team also wins the game - and you'll see a boost to your progression.