never blame anyone for anything

That's actually not quite true.

Assigning blame, via agency or otherwise, and the associated social or legal consequences are additional signals in the environment that influence and change behavior.

If the actions of an individual were involved in propagating some chain of events, then it's perfectly valid to respond to their involvement, via social stigma, punishment, etc, regardless of whether or not there is "agency". The knowledge and anticipation of a similar response changes future actor's behavior, with or without free will.

This discussion itself is exactly an example of this in practice. If there's no such thing as agency, then us talking about what someone should or shouldn't do, given whether there is free will, have any influence on anything, except that it does because interacting with these ideas themselves change behavior, with or without free will.

This is what people mean when they say we should just ignore the question of free will entirely, because it doesn't really factor into how we should design the social contract.