Real basketball players and managers would not stop to work in NBA because of the changes, it's how they earn money. BB is a game, change a large part of it and you could (i did not say for sure) lost half of the players.
Currently I know that from time to time I see users who are disatisfied with this game and pointing to the same things.
They feel that it is not competative for those who their time is not flexible.
There are those who point to the fact that it is not competative enough for new users.
There are those who are feeling that after a short while, as an old-user, this game is just doing the same (and even less - as training your drafted players is not exectued at higher leagues, etc.).
Those who stays at a game will be those who will find the game exiting even after few seasons.
New user will stay in this game after seeing that it is all in their own hands.
Those who will leave the game will be only those who find it interesting being part of a game that there is almost nothing to do and just celebrating a success due to their early coming into the game, and it will not be that big lost. Especially due to the above parts of newcomers.
BTW - managers at the NBA are there for the money, but the spectators ARE NOT. And they are still watching the game.
50K users is very few for this type of game which has many flavors and basically has very good design and concept.
The reason users losses interes too fast due to the reasons brought above.