I think the millionare card should not be removed but instead the millionare mission should be reworked in a way that rewards players a VARIABLE amount of starbits acording to the amount of fans they have. This could be done by having a minimum threshold (for example 70000 fans) and ofc a maximum (for example 200000 fans).
BUT, and this is the important part, keep the numbers updated over time so to make sure people are reinvesting in their accounts.
Another idea is that the millionare mission stops giving out starbits entirely and instead gives out 1 or 2 packs from an exclusive soulbound set of cards.
If this are not good ideas, im sure you can come out with others that makes sure that the players need to be heavily commited and invested before running the mission.