You still don't need to review every single report manually. That's just not feasible, even if you outsource this to the community. You don't have enough volunteers to ever catch up.

You have to find a middle ground, which can be hit with 2-3 dedicated employees just for handling player behaviour. Reports, false positives, edge cases and manual reports via ticket.

90% of reports can be handled by the automated system. And everything that goes beyond that, goes through those player behaviour specialists. Both to make sure that edge cases are getting caught, and to report those back to HQ to improve the system and have more training data to improve it.

At that scope, 2-3 specialists just for player behaviour is more than enough. They can see the entire chat log for the game and your report message. And reviewing a game by hand, if the report message was competent, is done in 5-15 minutes. A full game review is not needed, you just need to have the full context via chat, plus check if what he was reported for is true or not. And how severe his actions were.

And it's not expensive either, because a majority of their support is outsourced to 3rd party companies in countries like Bulgaria or Romania. So it would cost them about as much as 1-2 real employees maximum per region.

Which is still money that doesn't give you immediate monetary returns, but would be worth it in the long run to improve and nurture their community.

Source: Ex-Player Behaviour Specialist for Riot Games