People who don’t have everything focus their resources on building teams that they perceive as viable/enjoyable. They don’t all share your philosophy about how it’s all a means to an end regarding Kingdom Power.
In any case, anyone who has leveled a Legendary to Mythic 4x would want a refund for the 3x that suddenly became worthless. In some cases, like Store-bought Legendaries, that could have stiffed them out of $150. I think it’s safe to say they cannot make this change without a solid compensation plan in place.