The person you're responding to already said they ran a modestly sized site. What actual scale opens one up to abuse? If only the top 1% of sites need it, then it seems silly to say "everyone" needs it.
Stack Overflow was outside of the Cloudflare network for years, and anti-abuse was maybe 3 or 4 full-time jobs – much of which still needs to be done, because Cloudflare's anti-bot protection hasn't actually stopped it. Most UGC sites are not as big as Stack Overflow was at its peak.
errr... so anything related to UGC now has a lower bound of 3-4 FTE? Sure, I'll hire a team of content moderators next time I think about putting a comment form under my blog...