I'm a pretty junior contributor (I spent a couple years completing quests on StreetComplete and only have been adding new buildings, etc for a few weeks). I don't know a ton about how the organization is run, so I can only talk from my experiences. I've been able to upload changes which will be live before they will be reviewed. I know there are reviewers who go through areas regularly, but they definitely don't cover everywhere. I'm not sure if OSM has the ability to lockdown areas with frequent vandalism.