No, they didn't miss your point. You missed their point.
You're not criticizing the message, you're criticizing the messenger. Maybe Mozilla shouldn't be the one saying this. But are they wrong about Venmo?
By that logic, you shouldn't care about Mozilla because you can just download another browser.
But that's not true. Venmo and Firefox have an impact on the larger world, whether you use them or not. Both should be criticized. But criticizing the messenger does not excuse the behavior of the other.