I agree. The classic faction of NBA 2K fans exists, and they're pretty die-hard about their basketball. I feel pushing those fans away by ignoring that portion of real-life NBA basketball history is not going to do 2K any more favors.
If I had to be real, I think some classic team additions and generalized improvements (return of era filters, option for no three point line for 60's and 70's contests) could go a long way toward bringing true NBA fans back onto the 2K ship.
However, instead of improvements, 2K has regressed in this regard, so there's not a lot of incentive for me to come on board with a new 2K. Not only have the legends been more or less untouched, but it now appears the generic players cannot be properly edited on next gen as a means of correctly filling out the rosters (while also eliminating our ability to create our own).
I think turning an eye back to the league's history while re-introducing customization would be two tremendous ways to get 2K back on track.