The trick is to find out how to leverage the community for quality signals, and just support that with good foundations.
Spam filtering is done by corporations but they’re not all mega tech companies like Google. A lot of it is done at the network level, too.
DNS has also always been the prime example of a federated service that works so well we can rely on it as a public utility. Why hasn’t it been taken over by bad actors rapidly recycling their identities? It’s not because big tech has thousands of human agents monitoring it at great expense.