It’s usually not bad, that’s how you get lower spread (and in the US afaik it has to be as good as the current best offer: wikipedia “In the United States, accepting payment for order flow is only allowed if no other trading venue is quoting a better price on the National Market System.”).
What those market makers want is 1) capture the trading sentiment 2) not be rolled over by a massive trade (that’s the worst case for a market maker, a massive trade moves the market against them)
For them getting the retail flow is easy and beneficial to both parties.
Historically most of the revenue of low cost brokers has been through (lower) interest rates on balance.