Flagged Revisions are approved edit
1. Users that prefer to flag the revisions rather than do the revisions will take ages to go round every edit.
2. Users that prefer to edit rather than flag will get irritated having to wait for ages for their edits to be approved and will leave Wikipedia to go somewhere else.
3. At about the time when there are just a small group of users left, (there being more flaggers than editors) the editors will begin to struggle improving the entire encyclopedia by themselves.
4. The flaggers will think this is funny and will tease the editors by deliberately refusing every edit they make. As a result...
5. The encyclopedia never gets any better.
6. The remaining editors will leave.
What happens in the End? edit
Ending 1 (the Yay! one): Some flaggers will decide that they have done wrong and will become editors, paving the way for former editors to come back and for other flaggers to become editors again. Flagged Revisions are outlawed.
WHAT? That will not happen. This will.
Ending 2: All the flaggers are driven crazy by the lack of edits and will become vandal-flaggers, accepting every piece of vandalism there is.
And so, Wikipedia becomes a nightmare of vandals, sockpuppets, personal attacks and everything that disagrees with the Five Pillars.