this completely favours bot farms in the lower leagues. I don´t think that people that play manually would be lazy about playing brawls wich are the most rewarding in terms of effort.(especially for new players and lower leagues). Any new player can start being competitibe by earning reward cards that allow them to play the cards earned through brawls.
When the reward set came out, for me it was obvious that it meant to incentivize players to join clans and play brawls. How can it be a bad thing for the game? These cards are not monetized ever and they only contribute to a better, more complete experience.