As said before about in the post "BIG DATA is just data", a lot of information is worthless after 1 or 2 years and most after 5 years. Long term value data seems to be stored in IT systems' DBs rather successfully.

And I have so far always find important emails (notably because important topics are easily found emails chains and far more often than not in the dedicated meeting report).

Structuring data is cultural so you should rather learn to use the system used by your organization. Only super small teams and solo-founders need to think about how to store data. Most workers should follow their community to let other people find the information.

Folders, drawer, cabinet have been around for 3 centuries at least and imho, we are not gonna reinvent the wheel with this or that way to structure information.