Unfortunately, there aren't many good captcha systems that don't do the equivalent of what ReCaptcha does, because we're at a point where fingerprinting users i

Unfortunately, there aren't many good captcha systems that don't do the equivalent of what ReCaptcha does, because we're at a point where fingerprinting users is a strong signal to help identify contractors doing captchas on behalf of bots. Even some silicon valley products use captcha-breaker services. These services present themselves as sophisticated APIs but in reality they're just dispatching work to humans who accept pennies an hour at internet cafes; a competition with Amazon's mechanical turk for digital sweatshops. They're common and cheap and the tech industry feeds them. Undercutting the workforce doing the captcha busting is the only viable way to stop that. Your real alternative is to do the fingerprinting yourself.