There are bots that are very very cheap that solves captcha for you these days, I am sure the prevention doesn't come from captcha but from something else, hell I literally haven't solved captcha on this website for months now, I suppose when you solve enough of it the system makes you a person that is "human" and then you can use bots.

I don't know the ways they can go around and even if I did I wouldn't share it here for the reason that bad people may use it but in the end captcha itself is not enough, sure it is still better than not having it, not having it would result with a lot more trouble but see it as like a castle and captcha as it is walls, just because there is walls doesn't mean it will never be broken but surely it is better than not having any walls.