CAPTCHA is literally meant to be an automated Turing test.

It's right there in the name: "Completely Automated Public Turing test to tell Computers and Humans Apart"

CAPTCHA is Turing test with role reversal.

Computers try to figure out who is human and who is not. In Turing test humans try to who is human and who is not.

Some of the captchas I get lately have honestly made me think I'm probably not a human as far too often I can't make heads or tails of the letters.

At a certain point I just give up and refuse to use the worst sites that use this junk.

I just assumed the test was that if you can decode that mess, clearly you're a bot.