Payment for Order Flow

Payment for order flow has been a contentious black box ever since gamestops short squeeze. It seems to introduce a conflict of interest, because brokers are rewarded by the market maker when they send our trades over to them. On the other hand, brokerages say they always submit our trades such that we get the best execution. What's more, payment for order flow undoubtedly pave the way for brokerages to cut trade commissions to zero.