Rank up resources are becoming obsolete
I was just looking at rank up resources and the game's economy has changed a lot.
T1A was obsolete for 6 stars.
T4B became obsolete after taking a 6 star to R2.
T2A and T4C became obsolete after taking a 6 star to R3.
T5B became obsolete after taking a 6 star to R4.
We need to be able to sell T4C, T2A, and now even T5B. These will be useless resources for 7 stars that are already in the game and that's what players that have progressed further are now focusing towards since they already have all the 6 stars and ranked up who they need to.
I can think of a solution where the selling of rank up resources is locked by progression level if that allows us to sell these resources. It won't break the game economy and still keep summoners at lower progression from powering through content in order to develop their skill. Under developed skill leads to complaints when reaching more difficult content and we don't want ppl to give up and quit either.