Moderators on forums had to handle maybe 100 messages per day. They knew the context of each discussion thread and could make pretty well-considered and nuanced moderating decisions.

Twitter receives something like 500 million tweets per day. So if you had a million paid moderators, maybe they would be able to keep up with the sheer volume. And then you'd still get people arguing either side, too much or too little moderation/censorship. Corporate bias would be attributed, rightly or wrongly, just as it is now.