You either contribute to improving it, worsening it, or keeping it the same.

In two of those three cases, you are at fault (or continually become more at fault, more precisely, as the ratio of "how much it existed before you" shifts).

Contribute to keeping it the same? What does that mean? If the system has unfair policies, and you never personally enforce them or advocate for them and occasionally advocate against them, have you contributed to keeping it the same, and are you at fault?

You don't exist outside of the world, do you? If the most you ever do is "occasionally advocate against unfair policies," you certainly don't get to pat yourself on the back much for helping anything or anybody.

If you replace the word fault with "responsibility" or even a more neutral "influence" it's much more obvious, I think. You would clearly have less responsibility than the person advocating for said policies, but more than the person fighting them more vigorously or more effectively.

Nobody looks back and says "boy, I'm glad there were all those people who occasionally complained about Windows in the late 90s," they look back and respect and value the people who built alternatives instead.

Not getting to pat yourself on the back much for helping is one thing. Being at fault is fundamentally different.

We punish people who do bad things. We don't punish people who have neither helped nor done anything bad. We might we wish they had done better, but wishing and enforcing are very distinct mechanisms.