Perhaps with a worse conviction rate of the reports or by catching fewer cheaters. One major part of what makes this successful is that the reports by VACnet are high-quality and very often lead to convictions (i.e. they're not false positives). This keeps the humans who're actually judging engaged. From experience I found Overwatch fairly tedious if there's nothing fishy going on at all for ten cases or so, so participation rate has dropped over time.