I picked my list by going through the
Backpicks Top 40 greatest players of all time, generally our go-to for quality NBA analysis, to see who else hadn't won a title by age 24. Turns out it's about as common for them as it was to win one. I only looked at the top dozen or so.
We could keep going, if the point wasn't made. David Robinson (37). Nowitzki (32). Durant (28). Moses Malone (27). Rick Barry (30). Jason Kidd (37). Paul Pierce (30). Clyde Drexler (32). Ray Allen (32). Steve Nash, Chris Paul, Barkley, John Stockton, Patrick Ewing, Reggie Miller, Elgin Baylor - all never.
Your attempts to distinguish those as "players who underachieved", when they're the greatest players of all time, are really kinda weird.