system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU]If Black Widow put ALL of Shield's documents online how come none of the Avengers know Coulson is alive?
gpt
Are you kidding?  It's Nick Fury.  The classification isn't "levels" it's compartmentalized with no one person (including Fury) having access to every compartment.   SHIELD is essentially modeled after an insurgency because Fury's assumption was that the enemies he was facing would vastly outresource SHIELD and thus SHIELD had to have the capability to revert to a cell structure and fight as an insurgency to retake the earth itself.  In terms of structure don't think "US military" think "French Resistance" (or "Al-Qaeda" if you're not feeling generous).

There is no master access, there is no master key, there is no "everything" that Shield has.  Fury assumed anyone could be compromised, including himself.  Romanoff dumped a LOT of SHIELD's data.  She thought she had all because she thought she had the master key, but she only had a very good key because there is no master.

The closest thing to a master is Toolbox and Romanoff didn't have that.  Not that Fury would have completely trusted Coulson either.