Saying "I have no agency" is a defense technique to say "I have no blame".

If you don't have agency then you can't take blame.

This is the logic behind a victim mentality.

The victim mentality says, at the limit, "I have no agency and my oppressor is omnipotent".

How much of a victim you are is a spectrum.

It's never 0% or 100%.

In some extremely toxic situations it really is near 100%.

But in more typical day-to-day situations, often if we don't like the way it's going, we assume it's more than it actually is.

A victim mentality tends to fester and self-accelerate.

You tell yourself you don't have agency so you don't take the agency, so you have worse outcomes which you resent more, making you even more of an aggrieved victim.