There are a lot of reasons why some players are kind of forgotten or overlooked. First, time. It never stops moving and as new players come in, all but a handful fall out of the general discussion.
Then there’s the change in media. ESPN started in 1979 and prior to that, hard though it seems to believe now, you might get one NBA game per week on national TV.
And also some players just aren’t that good and don’t make that big of an impression. Most people wouldn’t remember Phil Jackson as a player if he hadn’t turned out to be a great coach.