This is my guess too, which is unfortunate. It would have been nice to at least have 3-4 nicknames we can choose from to at least make it "ours". It wouldn't have been *that* much more effort to record a few extra snippets for some lines.
I hope we can at least change it once we're in the league. If Spike Lee needs a name to sell his story, that's cool. But once we're in the NBA, we need our identity to be ours-- especially if Lee's story is no longer in play and there's no narrative benefit to having a forced nickname.
I hope this is the case and we will return to a more free-form but nuanced, realistic, and in-depth NBA career simulation. That said, there is nothing wrong with actual narrative elements and good execution and acting in an NBA sim. Having family members, entourage, agents, players, and GM's act out their parts with good deliveries to fill in an open narrative adds immersion to the experience-- so long as it doesn't railroad you into a story that isn't yours and represents "you" poorly.
Unfortunately, the MyCareer of the last couple of years was the opposite of that-- poor acting and execution and forcing your player to act in unprofessional and ridiculous ways, because... story? To say nothing about how GSW champion coach Steve Kerr would be forced out for Warriors rival coach Doc Rivers because again... story?
Having Harlan and crew expound on your player's achievements and background would be great. Having Ernie, Shaq, and Kenny share their takes about your player and then seque from that conversation into one of their usual ribbing sessions while working your player into their jokes would be amazing! Having superstars be interviewed by Doris Burke about the difficulty of being matched up against you and their thoughts on how to approach your game as a opponent, or on the playoff podium elaborating how they were defending you-- TAKE MY MONEY.
Now let us start Twitter beef with Hassan Whiteside written by Hassan Whiteside himself. THAT would be a proper MyCareer.