You are asserting that they don't work without explanation or evidence. Meanwhile it isn't clear why they wouldn't and indeed they appear to accomplish the stated goal of severely rate limiting scrapers.
Surely I don't need to explain how headless browsers work, bot proxies and distributed crawlers to you do I? If you haven't experienced this first-hand, I can understand. Maybe it warrants a blog post. But I can assure you, these don't work at scale, they might only stop the "less sophisticated" bots and maybe (just maybe) some unwanted spam.
> You are asserting that they don't work without explanation or evidence.
Oh, no, that isn't how it works — you made a claim first (albeit indirectly), with no evidence. It's on you
IIRC there was a blog post here on HN recently explaining in detail why Anubis doesn't keep out AI bots.