It's actually the opposite. The GM needs to be very careful with their roster, because if they aren't, the players could win too much. The players know that losing games means adding players who could take their job. They'd rather limp to the playoffs, not improve the team at all, and have a roster spot than bottom out, actually improve the team, and potentially lose their jobs. So you can't rely on players to help you improve the organization in that way.
Good tank GMs prune their tanking teams very carefully. Holland did that, but not as well as other teams.