I know there are some people out there that hate the microtransactions of MyCareer and just want to play singleplayer by creating a custom player and dropping them in MyNBA.
If you're one of those people, there's this website this guy has been working on called 2kDraft and helps create an upgrade system for doing just that.
You enter your attributes, play games, enter your stats, get xp, and use that xp to upgrade attributes and badges.
You can access it by going to 2kdraft.com. If you like what you see and want to provide feedback, report bugs, or suggest features, feel free to join the discord as well. The dev is very active and this sort of a dream project for him.
Have a good day.