companies try to exploit it for commercial gain.

Or when individuals exploit it for personal gain (influencers, resumes, etc), political interest groups exploit it for political gain, state actors exploit it for national security reasons, etc. Just look at less popular subreddits on Reddit and you’ll see a huge propensity toward echo chambers and manipulating people into thinking a certain way.

So yeah, people suck in large groups. Sometimes it’s regular people doing the sucking (e.g. bystander effect when some choose to gaslight/bully others), and sometimes it’s highly motivated groups of people doing the sucking (spam, misinformation, etc). But the larger the community gets, the more moderation is needed to counter the suck, and moderators themselves can add to the sucking.

I think the fediverse will struggle once it gets past a certain size, but hopefully I’m wrong. In the meantime, I (and probably others) are working on alternatives, so hopefully we’ll have solutions if the fediverse doesn’t work as expected.