Punishing vs rewarding in these cases are really just a matter of perspective. Yes, players using lower level cards will get less than they received previously if this change goes into effect, but really they were getting more than is sustainable for their cards in the past and it's just being "fixed" now.
But from the general perspective - not comparing it to a flawed previous system - the higher level your cards, the more rewards you earn - so you are rewarded for getting higher level cards.
Thanks for the reply. What aspect is unsustainable? Is it the rewards paid out or is it fluctuations in the card market?
I thought the fixed pool of rewards ensured sustainability, but I'm interested in learning why that is not the case, meaning we need to implement something like this. I love learning, so thanks for your insightful responses!